#include <bits/stdc++.h>

using namespace std;

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

inline int f(int m)
{
    return m/25 + m/5;
}

int cb(int p)
{
    int st = 1, dr = 100000000, m, last = -1;

    while(st<dr)
    {
        m = (st+dr)/2;

        if( f(m) >= p )
        {
            last = m;
            dr = m;

        }
        else st = m+1;
    }
    return last;
}

int main()
{
    int p;
    fin>>p;
    if(cb(p) == cb(p+1))
        fout<<-1;
    else
        fout<<cb(p);

}