#include <fstream>

using namespace std;

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

int nr0( int n )
{
    int             nr = 0;
    while( n >= 5 )
    {
        nr += n / 5;
        n /= 5;
    }
    return nr;
}

const int               L = 28;

int main()
{
    int             r = 0, pas = 0, p = 0;

    fin >> p;
    pas = 1 << L;
    while( pas != 0 )
    {
        if ( nr0( r + pas ) < p )
            r += pas;
        pas /= 2;
    }
    ++r;
    if( nr0( r ) != p )
        r = -1;
    fout << r;
    return 0;
}