#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int p;
int zero(int x)
{
    int ans = 0;
    while(x>=5)
        ans+=(x/=5);
    return ans;
}
int main()
{
    f >> p;
    int i = 1;
    int ok = 0;
    int m = 0;
    int s = (1<<28);
    while(i<=s)
    {
        m = (i+s)/2;
        if(zero(m)==p)
        {
            ok=1;
            g << m-(m%5);
            break;
        }
        else if(zero(m)<p) i=m+1;
        else if(zero(m)>p) s=m-1;
    }
    if(i>s) g << -1;
}