#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<stdlib.h>
#include<stdlib.h>
const int N = 1000;

int complong(int *a, int *b) {
int i = 0;
if (a[0] < b[0]) return -1;
if (a[0] > b[0]) return 1;
for (i = a[0]; i > 0; i--) {
    if (a[i] < b[i]) return -1;
    if (a[i] > b[i]) return 1;
}
return 0;
}

void readlong(int *a) {
int i=0,k=0;
char s[N+1];

gets_s(s,N+1);
a[0] = strlen(s);
for (i = 0; i <a[0]; i++) {
    a[a[0] - i] = s[i] - '0';
}

}

void writelong(int *a) {
int i = 0;
for (i = a[0]; i >= 1; i--)
    printf("%d", a[i]);

}

void main(void) {
int a[N + 5] = { 0 };
int b[N + 5] = { 0 };
int y[N + 1] = { 0 };

int m = 0;
int c = 0;
int i = 0;
char p = 0,g=0;
int j = 0;
int k = 0;
int cr = 0;
int u = 0;
int l = 0;
int q = 0;
printf("Enter the opearation");
scanf_s("%c", &p);
scanf_s("%*c", &p);
fflush(stdin);
switch (p) {
case'!':
   {
    printf("Enter the number to factorize ");
    scanf_s("%d", &l);
    int d = 1000000;
    int A[N] = { 1 };
    int  len = 1, r, s;
    for (k = 2; k <= l; k++) {
        i = 0; //
        r = 0; //
        while (i < len
            || r > 0) {
            s = A[i] * k + r;
            A[i] = s % d;
            r = s / d;
            i++;
        }
        len = i;
      }
      for (i = len - 1; i >= 0; i--)
        if (i == len - 1) printf("%d", A[i]);
        else printf("%.6d", A[i]);
        break;

     }

    case'-': {


    printf("Enter the first number ");


    readlong(a);
    printf("nEnter the second number ");
    readlong(b);


    if (complong(a, b) < 0) {
        printf("-");
        c = 0;
        for (i = 1; i <= b[0]; i++) {
            c = c + b[i] - a[i] + 10;
            b[i] = c % 10;
            if (c < 10) { c = -1; }
            else { c = 0; }
        }
        while ((b[b[0]] == 0 && b[0] > 1)) b[0] = b[0] - 1;
        writelong(b);
        break;
    }
    else {
        c = 0;
        for (i = 1; i <= a[0]; i++) {
            c = c + a[i] - b[i] + 10;
            a[i] = c % 10;
            if (c < 10) { c = -1; }
            else { c = 0; }
        }
        while ((a[a[0]] == 0 && a[0] > 1)) a[0] = a[0] - 1;
        writelong(a);
    }
    break;
    }



    case'+': {
    printf("Enter the first number ");


    readlong(a);
    printf("nEnter the second number ");
    readlong(b);
    if (a[0] > b[0]) {
        m = a[0];
    }
    else { m = b[0]; }
    c = 0;
    for (i = 1; i <= m; i++) {
        c = c + a[i] + b[i];
        a[i] = c % 10;
        c = c / 10;
    }
    if (c > 0) {
        m = m + 1;
        a[m] = c;
    }
    a[0] = m;
    writelong(a);
    break;
    }

    case'*': {

    printf("Enter the first number ");
    readlong(a);
    printf("nEnter the second number ");
    readlong(b);

    cr = 0;
    for (i = 1; i <= a[0]; i++) {
        for (j = 1; j <= b[0]; j++) {
            cr = a[i] * b[j];
            k = i + j - 1;
            while (cr > 0) {
                cr = cr + y[k];
                y[k] = cr % 10;
                cr = cr / 10;
                if (k > y[0]) y[0] = k;
                k = k + 1;
            }
        }
    }


    writelong(y);
    break;
    }










    case'^': { //возведение в степень
    int n = 0;
    printf("Enter the first number ");
    readlong(a);
    printf("nEnter the stepen ");
    scanf_s("%d", &n);

        cr = 0;
        for (i = 1; i <= a[0]; i++) {
            for (j = 1; j <= a[0]; j++) {
                cr = a[i] * a[j];
                k = i + j - 1;
                while (cr > 0) {
                    cr = cr + y[k];
                    y[k] = cr % 10;
                    cr = cr / 10;
                    if (k > y[0]) y[0] = k;
                    k = k + 1;

                    for (q = 1; q < N - 1; q++) {
                        m = y[q];
                        y[q] = a[q];
                        a[q] = m;
                    }

                }
            }
        }



    writelong(a);
    break;
  }



  default: printf("Incorrect operation"); break;



}


_getch();

 }

a^n = (a^{n/2})^2 = a^{n/2} * a^{n/2}

a^n = a^{n-1} * a