#include<stdio.h>

int main()
{ 
    int a=0;
    double PI4=0;
    for(int i=1;(1/i)>=0.000001;i+=2){
        a++;
        if(a%2==0){
            PI4-=(1/i);
        }else{
            PI4+=(1/i);
        }
    }
    printf("π的近似值为:%lf\n",PI4/4);
    return 0;
}