#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

long long zeros(long long m)
{
    long long put=5;
    long long N=0;
    while(m/put)
    {
        N+=m/put ;
        put*=5;
    }
    return N;
}

int main()
{   ifstream fin ("fact.in");
    ofstream fout ("fact.out");
    int P;
    long long st = 1;
    long long dr = 5e8;
    fin>>P ;
    while(st<=dr)
    {
        long long m=(st+dr)/2 ;
        long long N=zeros(m);
        if(N==P)
        {
            fout<<max(1LL, m-m%5);
            return 0;
        }
        else {
            if (N > P)
                dr = m - 1;
            else
                st = m + 1;
        }
    }
    fout<< "-1";
    return 0;
}