#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int main()
{
    int P;
    int N = 0;
    fin >> P;
    if(P == 0)
        fout << N;
    else
    {
        int  exp = 1;
        int i=0;
        while(i < P)
        {
            N += 5;
            if(N % 25 == 0)
                i++;
            i++;
        }
        fout << N;
    }
    return 0;

}