小白快哭了，这个循环嵌套怎么优化啊题目一直tle

Question

#include<stdio.h>
int main()
{
    long long n,i,ans,x;
    while(scanf("%lld",&n)!=EOF){
        if(n<5){
            printf("0");
            continue;
        }
        for(i=5;i<=n;i+=5){
            x=i;
            while(x%5==0){
                x/=5;
                ans++;
            }
        }
        printf("%lld",ans);
    }
    return 0;
}

Answer 1

ans 没赋初值