#include <stdio.h>
#include <math.h>
#include <string.h>

#define true 1
#define false 0
#define err -2000123000
#define max 9223372036854775807
#define PI 3.14159265358979323846

double myabs(double x) {
    if (x < 0) return -x;
    else return x;
}

double stod(char s[100]) {
    int i = 0, o = false, f = false;
    double sm = 0, d = 1;
    if (s[0] == '-') {
        o = true;
        i++;
    }
    if (s[0] == '\0' || s[0] == '\n') return 0;
    while (s[i] != '\0' && s[i] != '\n') {
        if (f) d *= 10;
        if (s[i] >= '0' && s[i] <= '9') sm = sm * 10 + (s[i] - '0');
        else if (s[i] == '.' && !f) f = true;
        else return err;

        if (sm >= max / 100) return err;
        i++;
    }
    if (o == true) return -1 * sm / d;
    else return sm / d;
}

void problem2() {
    printf("vvedite x and eps\n");
    double x, eps, sum = 0, fc = 1;
    char s1[1000] = {'\0'}, s2[1000] = {'\0'};
    scanf("%s %s", &s1, &s2);
    x = stod(s1);
    eps = stod(s2);
    if (x == err || eps == err) {
        printf("error");
        return;
    }
    if (eps <= 0) {
        printf("err: epsilon should be more than 0");
        return;
    }
    if (myabs(x) >= 1000) {
        printf("err: x too big");
        return;
    }
    printf("right sin is %lf\n", sin(x));
    while (x > PI + 0.1) x -= 2 * PI;
    while (x < PI - 0.1) x += 2 * PI;
    double z = x, xx = x;
    int i = 1;
    while (myabs(z) >= eps) {
        if ((i / 2) % 2 == 0) sum += z;
        else sum -= z;
        fc *= (i + 1) * (i + 2);
        /* if (xx>max/(x*x) || (x*x)>max/(xx) || fc>max/((i+1)*(i+2)) || ((i+1)*(i+2))>max/fc)
         {
             printf ("Run time error");
             return 0;
         }*/
        xx *= x * x;
        z = xx / fc;
        i += 2;
    }
    printf(" my  sin  is %lf\n", sum);
    printf(" actual epsilon is  %lf\n", myabs(sin(x) - sum));
    printf("should be less than %lf\n", eps);
    printf("n = %d", i / 2 + 1);
}