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

int main(void){

	int n, i, count=0;
	double x,y,r;
	srand((unsigned)time(NULL));
	printf("How many trials? ");
	scanf("%d",&n);
	for(i=0;i<n;i++){
		x = rand()/(RAND_MAX + 1.0);
		y = rand()/(RAND_MAX + 1.0);
		if(y<sin(M_PI*x)) count++;
	}
	r = (double)count/n;
	printf("Result is %f (Error: %f)\n",r, r-2/M_PI);
	return 0;
}