//Cautare binara dupa ideea originala a lui Mihai Patrascu
#include <fstream>
using namespace std;
int aew(int go)
{
    int r = 0;
    while(go>=1) r+=go/5, go/=5;
    return r;
}
int main()
{
    int n, step, i, we;
    ifstream in("fact.in"); in >> n; in.close();
    for (step = 1; step < 2000000; step <<= 1);
    for (i = 1; step; step >>= 1)
    {
        we = aew(i+step);
        if (i + step < 2000000 && we < n) i += step;
    }
    ofstream out("fact.out");
    if (we==n) out << i + 1;
    else
    out << "-1";
    out.close();
    return 0;
}