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

double f(double x)
{   double fx, pi = 3.1415926535897932;
    fx = sin(pi*x);
    return (fx);
}

double findint(double xl, double xr)
{   double h, x1, x2, x3, find;
    h = xr - xl;
    x1 = xl + h*(1.0-sqrt(0.6))/2.0;
    x2 = xl + h/2.0;
    x3 = xl + h*(1.0+sqrt(0.6))/2.0;
    find = h*(5.0*f(x1)+8.0*f(x2)+5.0*f(x3))/18.0;
    return (find);
}

main(int argc, char** argv)
{   double xl, xr, h, total=0.0;
    int s, m;

    printf("Input the two end points for the integration -> ");
    scanf("%lf %lf",&xl,&xr);
    printf("Please enter the number of subintervals -> ");
    scanf("%d",&s);
    printf("xl and xr: %f %f \n",xl,xr);
    h = (xr-xl)/s;
    xr = xl + h;
    for (m = 0; m < s; m++) {
        total = total + findint(xl,xr);
        xl = xr;
        xr = xl + h;
    }
    printf("The estimate of the integral is %f \n",total);
}