例1-1

#include<stdio.h>
int main(void)
{
    int n;
    int factorial(int n);


    scanf("%d",&n);
    printf("%d\n",factorial(n));
    

    return 0;
}

int factorial(int n)
{
    int i,fact=1;


    for(i=1;i<=n;i++)
        fact=fact*i;


    return fact;
}