输入一个正整数n，n<=20，求n的阶层的C语言编程

#include <stdio.h>

int main()
{
int n, i;
long long factorial = 1;

printf("请输入一个正整数n：");
scanf("%d", &n);

for (i = 1; i <= n; i++) {
factorial *= i;
}

printf("%d的阶乘为%lld\n", n, factorial);

return 0;
}