求方差，学校的oj平台总是WA，不知道哪里错了

Question

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int n,sum=0,fact=0;
    double x;
    scanf("%d",&n);
    for(int i=1; i <= n; i++){
        scanf("%lf",&x);
        sum += x;
        fact += x*x;
    }
    sum = sum/n;
    double s;
    s = fact - n*sum*sum;
    printf("%f",s);


    return 0;
}