#include <stdio.h>
#include <stdlib.h>
#define NP 50000000
int main(){
    int i;
    float x,y,pi;
    long n = 0;
    for(i = 0; i < NP; i++){
          x = (float)rand()/(float)RAND_MAX;
          y = (float)rand()/(float)RAND_MAX;
          if( (x*x + y*y) <= 1.0) n++;
    }
    pi = 4.0*(float)n/(float)NP ;
    printf("pi:%f\n", pi);
    system("PAUSE");
}