#include<fstream>
using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int nr_zero(int n)
{
    int s=0;
    while(n>=5)
    {
        s+=n/5;
        n=n/5;
    }
    return s;
}

int cautbin(int p)
{
    int rez=-1, zero;
    int st=1, dr=1e9;
    while(st<=dr)
    {
        int m=(st+dr)/2;
        int zerouri=nr_zero(m);
        if(zerouri>=p)
        {
            rez=m;
            zero=zerouri;
            dr=m-1;
        }
        else
        {
            st=m+1;

        }
    }
    if(zero!=p)
    {
        rez=-1;
    }
    return rez;
}


int main()
{
    int p;
    fin >> p;
    fout << cautbin(p);
    return 0;

}