#include <fstream>

using namespace std;

int main()
{
    ifstream in("fact.in");
    ofstream out("fact.out");
    long long p, mij, st=1, dr=999999999999999999999,x=5,cnt=0,minn=999999999999999999999;
    in >> p;
    while(st <= dr)
    {
        mij = (st + dr) / 2;
        x = 5;
        cnt = 0;
        while(mij / x > 0)
        {
            cnt = cnt + mij / x;
            x *= 5;
        }
        if(cnt < p)
            st = mij+1;
        else
        {
          if(minn >= mij && cnt == p)
              minn = mij;
          dr = mij-1;
        }
    }
    if(minn == 999999999999999999999)
      out << -1;
    else
      out << minn;
    return 0;
}