#include<stdio.h>
#include<math.h>
#include<windows.h>
int main(void)
{
    int i,n;
    double factorial;
    printf("please input the number");
    scanf("%d",&n);
    factorial=1;
    for(i=1;i<=n;i++)
        factorial=factorial*i;
    printf("%d!= %.0f\n",n,factorial);
    system("pause");
}