#include <bits/stdc++.h>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int n,mijloc,p,a,st,dr;
int nrzero(int x)
{
    int rasp=0;
    for(int i=5; i<=x; i*=5) rasp+=x/i;
    return rasp;
}
int main()
{
    fin>>p;
    dr=1<<30;
    st=0;
    while(dr-st>1)
    {
        mijloc=st+(dr-st)/2;
        a= nrzero(mijloc);
        if(a==p)
        {
            if(mijloc%5==0)fout<<mijloc;
            else fout<<mijloc-mijloc%5;

            return 0;
        }
        if(a>p)dr=mijloc;
        else st=mijloc;

    }
    if(nrzero(st)==p)fout<<mijloc;
    else fout<<-1;
    return 0;
}