#include <fstream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");

int zero(int n)
{
    int nr0=0;
    while(n!=0)
    {
        nr0+=n/5;
        n/=5;
    }
    return nr0;
}

int main()
{
    const int L=30;
    int nr0,r=0,pas=1<<L;

    in>>nr0;
    while(pas!=0)
    {
        if(zero(r+pas)<nr0)
            r+=pas;
        pas/=2;
    }

    if(zero(r+1)==nr0)
        out<<r+1;
    else
        out<<-1;
    return 0;
}