#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI_TRUE 3.14159265358979323846



int main(void){
    int n = 100000; 
    int count = 0;
    int i;
    double x,y;
    double PI,gosa;
    for(i=0;i<n;i++){
     x = (double) rand()/ RAND_MAX;
     y= (double) rand() /RAND_MAX;
     if(x*x+y*y<=1.0){
     	count++;
     }
    }
    PI=4.0*count/n;
    gosa=fabs(PI-PI_TRUE)/PI_TRUE*100;
    printf("円周率 = %f\n", PI);
    printf("元の円周率との誤差= %f%%\n", gosa);
    
	return 0;
}