#include<stdio.h>
 
 int main()
{
    int n, m = 1, pro;
    long fact(int);//实现阶乘的函数
    printf("Input n:");
    scanf_s("%d", &n);
    for (; m <= n; m++)
        pro = fact(m);
    printf("%d!=%ld\n", n, pro);
}
 
long fact(int n)
{
    static long pro = 1;//pro即product---乘积
    pro = pro * n;
    return(pro);
}