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#include <iostream>
#include <math.h>
#include <string>
using namespace std;

#define MAXDIGITS   1000        /* maximum length bignum */
#define PLUS        1       /* positive sign bit */
#define MINUS       -1      /* negative sign bit */

struct BigInt
{
    char digits[MAXDIGITS];         /* represent the number */
    int signbit;            /* 1 if positive, -1 if negative */
    int lastdigit;          /* index of high-order digit */

    BigInt operator+(BigInt& b) {
        BigInt c;
        add_bignum(this, &b, &c);
        return c;
    }

    BigInt operator -(BigInt& b) {
        BigInt c;
        subtract_bignum(this, &b, &c);
        return c;
    }
    BigInt operator << (BigInt& b) {}
    BigInt operator >>(BigInt& b) {}

    bool operator < (BigInt& b)
    {
        return compare_bignum(this, &b) > 0;
    }
    bool operator > (BigInt b)
    {
        return compare_bignum(this, &b) < 0;
    }
    bool operator == (BigInt b)
    {
        return compare_bignum(this, &b) == 0;
    }
    bool operator != (BigInt b) {
        return !(*this == b);
    }

    int max(int a, int b)
    {
        if (a > b) return(a);
        else return(b);
    }

    void add_bignum(BigInt *a, BigInt *b, BigInt *c)
    {
        int carry;          /* carry digit */
        int i;              /* counter */

        initialize_bignum(c);

        if (a->signbit == b->signbit) c->signbit = a->signbit;
        else {
            if (a->signbit == MINUS) {
                a->signbit = PLUS;
                subtract_bignum(b, a, c);
                a->signbit = MINUS;
            }
            else {
                b->signbit = PLUS;
                subtract_bignum(a, b, c);
                b->signbit = MINUS;
            }
            return;
        }

        c->lastdigit = max(a->lastdigit, b->lastdigit) + 1;
        carry = 0;

        for (i = 0; i <= (c->lastdigit); i++) {
            c->digits[i] = (char)(carry + a->digits[i] + b->digits[i]) % 10;
            carry = (carry + a->digits[i] + b->digits[i]) / 10;
        }

        zero_justify(c);
    }

    void int_to_bignum(int s, BigInt *n)
    {
        int i;              /* counter */
        int t;              /* int to work with */

        if (s >= 0) n->signbit = PLUS;
        else n->signbit = MINUS;

        for (i = 0; i < MAXDIGITS; i++) n->digits[i] = (char)0;

        n->lastdigit = -1;

        t = abs(s);

        while (t > 0) {
            n->lastdigit++;
            n->digits[n->lastdigit] = (t % 10);
            t = t / 10;
        }

        if (s == 0) n->lastdigit = 0;
    }

    void int_to_bignum(int s)
    {
        int_to_bignum(s, this);
    }

    void str_to_bignum(string num)
    {
        for (int i = 0;i < MAXDIGITS; i++) {
            digits[i] = 0;
        }
        if (num[0] != '-') {
            for (auto it = num.crbegin(); it != num.crend(); it++) {
                digits[it - num.crbegin()] = *it - '0';
            }
            lastdigit = num.size() - 1;
            signbit = PLUS;
        }
        else {
            auto end = num.crend();
            end--;
            for (auto it = num.crbegin(); it != end; it++) {
                digits[it - num.crbegin()] = *it - '0';
            }
            lastdigit = num.size() - 2;
            signbit = MINUS;
        }

    }

    void initialize_bignum(BigInt *n)
    {
        int_to_bignum(0, n);
    }

    void subtract_bignum(BigInt *a, BigInt *b, BigInt *c)
    {
        int borrow;         /* has anything been borrowed? */
        int v;              /* placeholder digit */
        int i;              /* counter */

        initialize_bignum(c);

        if ((a->signbit == MINUS) || (b->signbit == MINUS)) {
            b->signbit = -1 * b->signbit;
            add_bignum(a, b, c);
            b->signbit = -1 * b->signbit;
            return;
        }

        if (compare_bignum(a, b) == PLUS) {
            subtract_bignum(b, a, c);
            c->signbit = MINUS;
            return;
        }

        c->lastdigit = max(a->lastdigit, b->lastdigit);
        borrow = 0;

        for (i = 0; i <= (c->lastdigit); i++) {
            v = (a->digits[i] - borrow - b->digits[i]);
            if (a->digits[i] > 0)
                borrow = 0;
            if (v < 0) {
                v = v + 10;
                borrow = 1;
            }

            c->digits[i] = (char)v % 10;
        }

        zero_justify(c);
    }

    int compare_bignum(BigInt *a, BigInt *b)
    {
        int i;

        if ((a->signbit == MINUS) && (b->signbit == PLUS)) return(PLUS);
        if ((a->signbit == PLUS) && (b->signbit == MINUS)) return(MINUS);

        if (b->lastdigit > a->lastdigit) return (PLUS * a->signbit);
        if (a->lastdigit > b->lastdigit) return (MINUS * a->signbit);

        for (i = a->lastdigit; i >= 0; i--) {
            if (a->digits[i] > b->digits[i]) return(MINUS * a->signbit);
            if (b->digits[i] > a->digits[i]) return(PLUS * a->signbit);
        }

        return 0;
    }

    void zero_justify(BigInt *n)
    {
        while ((n->lastdigit > 0) && (n->digits[n->lastdigit] == 0))
            n->lastdigit--;

        if ((n->lastdigit == 0) && (n->digits[0] == 0))
            n->signbit = PLUS;  /* hack to avoid -0 */
    }

    void print_bignum()
    {
        int i;

        if (signbit == MINUS) printf("- ");
        for (i = lastdigit; i >= 0; i--)
            printf("%c", '0' + digits[i]);

        printf("\n");
    }

};


int main()
{
    BigInt test1;
    test1.str_to_bignum("123456789012345678901234567890");
    test1.print_bignum();
    BigInt test2;
    test2.str_to_bignum("-123456789012345678901234567890");
    test2.print_bignum();

    test2 = test2 + test1;
    test2.print_bignum();

    setlocale(LC_ALL, "Russian");
    int a, b;
    cout << "Enter a:"; cin >> a;
    cout << "Enter b:"; cin >> b;
    BigInt n1, n2, n3, zero;



    n1.int_to_bignum(a);
    n2.int_to_bignum(b);

    n3 = n1 + n2;
    printf("Сочетание= ");
    n3.print_bignum();

    n3 = n1 - n2;
    cout << "Вычитание= ";
    n3.print_bignum();

    cout << "б меньше а? Ответ: " << (n2 < n1) << endl;

    cout << "б больше а? Ответ: " << (n2 > n1) << endl;

    cout << "б равно а? Ответ: " << (n2 == n1) << endl;

    cout << "Не равно ли б переменной а? Ответ: " << (n2 != n1) << endl;

    system("pause");
    return 0;
}