#include<fstream>
#include<iostream>
using namespace std;
int zero(int n)
{
    int contor=0;
    while(n>=5)
    {
        contor += n/5;
        n/=5;
    }
    return contor;
}
int caut(int p)
{
    int i=0,pas=1<<30;
    while(pas!=0)
    {
        if(zero(i+pas)<p)
            i+=pas;
        pas /= 2;
    }
    return i+1;
}
ifstream in("fact.in");
ofstream out("fact.out");
int main()
{
    int n,p;
    in>>p;
    n = caut(p);
    if(zero(n)==p)
        out<<n;
    else
        out<<"-1";
    in.close();
    out.close();
}