Bisection method for equations

bis.c

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

double f(double x) {
    double result = (x * x * x) - (3 * x) - 1;

    return result;
}


int main(void) {
    double a, b, c;
    double eps = 0.0001;

    printf("a,b=");
    scanf("%lf,%lf", &a, &b);

    do {
        c = (a + b) / 2;

        if (f(c) == 0) {
            break;
        }

        if (f(b - a) < 0) {
            b = c;
        } else {
            a = c;
        }
    } while (fabs(a - b) > eps);

    printf("x=%f\n", c);

    return 0;
}