#include <iostream>
using namespace std;
int main() {
int n;
cin >> n;
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++)
{
if(i>0 && i<n-1 && j>0 && j<n-1)
{
cout<<"O";
}
else
cout<<"*";
}
cout<<endl;
}
return 0;
}
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