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

main(){
    float x, a, sum, eps=1e-4;
    int i=1, lim=1000;
    do {
    printf("Input x [-1; 1]: ");
    scanf("%f", &x );
    }   while(x > 1 || x < -1);
    a = sum = 1;
    for (i; fabs(a) >= eps ; i++){

        a*= x*x/(2*i)/(2*i-1);
        sum+=a;

        if (i > lim) {
            printf("divergents");
            break;
        }
    }
if (i <= lim)
    printf("ch(%.1f): %f\ntest:\t %f" , x, sum, cosh(x));
}