Помощ по ООП /2 задачи/

[Ge7OverHere]

#include <iostream.h>
int main()
{cout<<"n= ";
int n;
cin>>n;
if (!cin)
{cout<<"Error. Bad input! \n";
return 1;
}
if (n<=0)
{
cout<<"Incorrect input! \n";
return 1;
}
int fact=1;
for (int i=1; i<=n; i++)
fact=fact*i;
cout<<n<<"! = "<<fact<<"\n";
return 0;
}