include <iostream>
using namespace std;
int main()
{
int a(0),P(1);
while(a<=20):
P*=a;
a+=2;
}
cout<<P;
return 0;
include <iostream>
using namespace std;
int main()
{
int a(0),P(1);
while(a<=20):
{
P*=a;
a+=2;
}
cout<<P;
return 0;
}