#include <iostream>
#include <fstream>
using namespace std;

long long ncz(long long n)
{
    long long s=0,p5=5;
    while(p5<=n)
    {
        s+=n/p5;
        p5*=5;
    }
    return s;
}

int main()
{
    long long m,nc,st=0,dr=1000000000,p;
    ifstream fin("fact.in");
    fin>>p;
    while(st<=dr)
    {
        m=(st+dr)/2;
        nc=ncz(m);
        if(p<=nc)dr=m-1;
        else st=m+1;
    }
    ofstream fout("fact.out");
    if(p==0)fout<<1;
    else
    if(ncz(st)==p)
            fout<<st;
    else
        fout<<-1;
    return 0;
}