#include <fstream>

using namespace std;

int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");

    long int p;
    f >> p;

    if(p == 0)
    {
        g << 1;
    }
    else
    {
        long int s = 1;
        long int d = 10000000000000;
        bool b = false;
        while(s <= d)
        {
            long int mij = (s+d)/2;
            long int t = 5;
            long int nr0 = 0;
            while(t <= mij)
            {
                nr0 += mij/t;
                t*=5;
            }
            if(nr0 == p)
            {
                b = true;
                while(mij % 5 !=0)
                    mij--;
                g << mij;
                break;
            }
            else
            {
                if(p < nr0)
                    d = mij-1;
                else
                    s = mij + 1;
            }
        }
        if(!b)
    {
            g << -1;
        }
    }

    return 0;
}