#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
ifstream f("fact.in");
ofstream g("fact.out");
ull n,nr,i;
int main()
{
    f>>n;
    if(n==0)
        g<<1;
    else{
    i=5;
    while(nr<n)
    {   ull x=0,y;
        y=i;
        while(y%5==0){
            x++;
            y/=5;
        }
        nr=nr+x;
        i+=5;
    }
    if(nr==n)
    g<<i-5;
    else g<<-1;
    }
    return 0;
}