#include <fstream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int zero(int n)
{
    int nr=0;
    while(n>=5)
    {
        nr+=n/5;
        n/=5;
    }
    return nr;
}
int calcul(int p)
{
    int n=0,pas=1<<30;
    while(pas!=0)
    {
        if(zero(n+pas)<p)
        n+=pas;
        pas/=2;
    }
    return 1+n;
}
int main()
{
    int p;
    in>>p;
    if(zero(calcul(p))!=p)
    out<<-1;
    else out<<calcul(p);
    return 0;
}