#include <cstdio>
#include <fstream>
#include <iostream>
using namespace std;
int nr_5(int n)
{
    int p5 = 5,s=0;
    while(p5<=n)
        s+=n/p5,p5*=5;
    return s;
}
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    int li = 1 , lf = INT_MAX , p ;
    f >> p ;
    while(li<=lf)
    {
        int mij = (li+lf)/2;
        int nr_0=nr_5(mij);
        if(nr_0>=p)
            lf=mij-1;
        else
            li=mij+1;
    }
    if(nr_5(li)==p)
        g << li ;
    else
        g << -1;
    return 0;
}