7-15 calculation of PI

According to the following relation , Find the value of pi , Until the value of the last item is less than the given threshold .
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Input format ：
The input gives less than... On one line 1 The threshold of .
Output format ：
Output the approximate PI satisfying the threshold condition in one line , Output after decimal point 6 position .
sample input ：

0.01

sample output ：

3.132157

Code thinking ：

#include <stdio.h>
int main()
{
    double PI=1;
    double t;
    double num=1.0;
    int i=1;
    scanf("%lf",&t);
    while(num>t) // Stop until the last item is less than the threshold 
    {
        num=num*i/(i*2+1); // The numerator in each fraction is a factorial , The denominator is an arithmetic sequence 
        PI+=num;
        i++;
    }
    printf("%.6f\n",PI*2);
    return 0;
}