#include <iostream>
#include <fstream>
using namespace std;
long long  p,l,r,m;
long long  vczalf(long long  n)
{
    long long  k=0;
    while(n>0){k+=n/5; n/=5;}
    return k;
}
int main()
{
    ifstream fin ("fact.in");
    ofstream fout ("fact.out");
    fin>>p;
    l=1;
    r=1ll<<60;
    long long  best=-1;
    while(l<=r)
    {
        m=(l+r)/2;
        if(vczalf(m)>=p){best=m;r=m-1;}
        else l=m+1;
    }
    if(vczalf(best)==p)fout<<best;
    else fout<<"-1";
    fout<<"\n";
    return 0;
}