#include <iostream>
#include <fstream>

using namespace std;

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

int cif( int n )
{
    int r = 0;
    while( n >= 5 )
    {
        r += n/5;
        n /= 5;
    }

    return r;
}

int cb( int n )
{
    int r = 0, pas = 1 << 29;
    while( pas != 0 )
    {
        if( cif( r + pas ) < n )
            r += pas;
        pas /= 2;
    }
    ++r;

    return r;
}


int main()
{
    int n, m;
    fin >> n;
    m = cb(n);
    if( cif(m) == n )
        fout << m;
    else
        fout << -1;

    return 0;
}