#include <iostream>
#include <fstream>

using namespace std;

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

int zero( int x)
{
    int nr=0;
    while(x>=5)
    {
        nr+=x/5;
        x/=5;
    }
    return nr;
}

int main()
{
    int p, i, pas=1<<28, r=0;
    in>>p;
    while(pas!=0)
    {
        if(zero(r+pas)<p)
            r+=pas;
        pas/=2;
    }
    r++;
    if(zero(r)==p)
        out<<r;
    else
        out<<-1;
    return 0;
}