Contest1258/E.cpp

#include<iostream>

using namespace std;

int main(int argc, char const *argv[]) {
    for (int n; cin >> n;) {
        if (n == 1)
            cout << "O" << endl;
        else {
            for (int i = 0; i < n; i++)
                cout << "O";
            cout << endl;
            for (int i = 0; i < n - 2; i++) {
                cout << "O";
                for (int j = 0; j < n - 2; j++)
                    cout << " ";
                cout << "O" << endl;
            }
            for (int i = 0; i < n; i++)
                cout << "O";
            cout << endl;

        }
        cout << endl;
    }
    return 0;
}