#include <bits/stdc++.h>

using namespace std;
long long n, st=1, dr=1000000000;
int check(long long nr)
{
   long long p=5, nrzero=0;
   while(p<=nr)
   {
    nrzero+=nr/p;
    p*=5;
   }
   return nrzero;
}
int main()
{
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin>>n;

    while(st<=dr)
    {
        long long mij=(st+dr)/2;

            if(check(mij)<n)
                st=mij+1;
            else dr=mij-1;

    }
    //cout << check(st) << " ";
    if(check(st)==n)
        cout<<st;
    else cout<<-1;
    return 0;
}