#include <fstream>

using namespace std;

bool is5pow(long x)
{
    long y = 1;
    while(y < x)
    {
        y *= 5;
    }

    if(x == y)
        return true;
    return false;
}
int main()
{
    long p, pow, zeros, i;

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

    fin>>p;
    fin.close();
    if(p == 0)
        fout<<1;
    else
    {
        for(i = 0, zeros = 0, pow = 0; zeros <= p; i += 5)
        {
            if(!is5pow(i))
                ++zeros;
            else
            {
                ++pow;
                zeros += pow;
            }
        }
        if(zeros == p + 1)
            fout<<i - 5;
        else
            fout<< -1;
    }
    fout.close();
    return 0;
}