5x5.cpp

gistfile1.txt

#include <iostream>

using namespace std;

int main(){
    int a, b;
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    cin >> a;
    b = a/10;
    if(a==5) 
        cout << 25;
    else
        cout << b*(b+1) << 25;
}