#include <iostream>
#include <fstream>

using namespace std;

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

const int L=30;
int p;

int zero (int y)
{
    int n=0;
    while(y>=5)
    {
        n+=(y/=5);
    }
    return n ;
}

void caut_bin( )
{
    int pas=1<<L , r=0;
    while(pas!= 0)
    {
        if(zero(r+pas) < p)
            r+=pas;
        pas/=2;
    }
    if(zero(r+1+pas) != p )
        out<<"-1";
    else
    out<<r+1;
}

int main()
{
    in>>p;
    caut_bin( );
    return 0;
}