关键在于最后如何筛选出i=10000,20000,30000...100000时的π值（C语言)

#include<stdio.h>
int main(){
    double PI=0, sign=-1;
    int i=1;
    while (i <= 100000){
        sign *= -1;
        PI += sign/ (double)(2 * (i++) - 1);
        if(i%10000==1) printf("%d %f\n",i-1,4*PI);
    }
    printf("%f\n",PI*4);
    return 1;
}