#include <iostream>
#include <fstream>

using namespace std;

const int VMAX=500000000;


int nr_zero(int n){

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

int main()
{
    fstream fin("fact.in");
    ofstream fout("fact.out");
    int p;
    fin >> p;
    int st=1;
    int dr=VMAX;
    while(st<dr)
    {
        int m=(st+dr)/2;
        if(nr_zero(m)>=p)
        {
            dr=m;
        }
        else
        {
            st=m+1;
        }
    }
    if (nr_zero(st) != p)
    {
        st = -1;
    }
    fout<<st;
    fin.close();
    fout.close();
    return 0;
}