#include <iostream>
#include <fstream>

using namespace std;

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

int P;

int zero(int x)
{
    int i,k;
    k=0;
    for(i=5;i<=x;i*=5)
        k+=x/i;
    return k;
}

int search(int stg, int dr)
{
    int m,x;
    while(stg<=dr)
    {
        m=(stg+dr)/2;
        x=zero(m);
        if(x==P)
            return m;
        if(P>x)
            stg=m+1;
        else
            dr=m-1;
    }
}

int main()
{
    fin>>P;
    int i;
    i=search(1,100000000);
    while(i%5!=0)
        i--;
    if(P==0)
        i=1;
    if(i)
        fout<<i;
    else
        fout<<-1;
    fin.close();
    fout.close();
    return 0;
}