#include <iostream>
#include  <fstream>
using namespace std;

ifstream in ("fact.in");
ofstream out("fact.out");
int p;
int zero (int n)
{
    int sum=0;
    /*
    for(int i=5;i<=n;i*=5)
        sum+=n/i;
    */
    while(n>=5)
    {
        //n/=5;
        sum += (n/=5);
    }
    return sum;
}
int cautb(int p)
{
    int i,pas=1<<30;
    for(i=0 ; pas ; pas>>=1)
        if(zero(i+pas) < p)
            i += pas;
    return 1 + i;
}
int main()
{
    in>>p;
    int r = cautb(p);
    if(zero(r)==p)
        out<<r;
    else
        out<<-1;
    return 0;
}