#include<iostream>
using namespace std;
int data_input();
int jiecheng(int n);
int sum=1;
void main()
{
int sum=1;
cout<<"输入数据:"<<endl;
int n;
cin>>n;
cout<<n<<"!="<<jiecheng(n)<<endl;
system("pause");
main();
}
int jiecheng(int n)
{
if(n==0)
return 1;
else
return(n*jiecheng(n-1));
}