#include <iostream>
#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int nr0(int x)
{
    int nrd0=0,pi=5;
    while(pi<=x){
    nrd0+=x/pi;
    pi*=5;}
    return nrd0;
}
int s,d,n,p;
int bs(int s,int d,int x)
{
    int m;
    while(s<=d)
    {
        m=s+(d-s)/2;
        if(nr0(m)==p)
            if(m==s) return m;
            else if(nr0(m-1)!=p) return m;
                 else d = m - 1;
        else if(nr0(m)>p) d = m - 1;
             else s = m + 1;
    }
    return -1;
}
int main()
{
    f>>p;
    if(p==0)g<<1;
    else
    g<<bs(1,100000000,p);
    return 0;
}