#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int P;
int zerouri(int x)
{
    int ans=0;
    while(x>=5)
        ans+=(x/=5);
    return ans;
}
int main()
{
    int r=0, pas=1<<28, p;
    f>>p;
    while(pas)
    {
        if(zerouri(r+pas)<p)
            r+=pas;
        pas/=2;
    }
    r++;
    if(zerouri(r)!=p) r=-1;
    g << r;
    return 0;
    f.close();
    g.close();
}