#include <bits/stdc++.h>
using namespace std;
long long l,r,p,m,u;
int n(int a)
{
    int i=5,t=0,k=0;
    while(i<=a)
    {
        k = k+a/i;
        i=i*5;
    }
    return k;
}
int main()
{
    freopen("fact.in","rz",stdin);
    freopen("fact.out","w",stdout);
    cin >> p;
    if (p == 0)
    {
        cout << 1;
        return 0;
    }
    u=0;
    l=1;
    r=5*p;
    while(l<=r)
    {
        m=l+(r-l)/2;
        if (n(m) == p)
        u=1;

        if (n(m)>=p)
        r=m-1;
        else l=m+1;
    }
    if (u)
    cout<<l;
    else cout<<-1;
  return 0;
}