function check(name, num, callback) {
  https.get("https://api.mojang.com/users/profiles/minecraft/" + name + "?at=" + num, function(resp) {
    callback(resp.statusCode === 200);
  });
};

function track(name, a, b, lastfail) {
  a = a || 1263146630; // notch sign-up
  b = b || Math.floor(Date.now()/1000);
  lastfail = lastfail || 0;

  if(a === b) {
    check(name, a, function(ok) {
      if (ok && lastfail === a-1) {
        console.log("found:", new Date(a*1000).toUTCString());
      } else {
        if (lastfail === 0) {
          console.log("target is <= " + a);
        } else {
          console.log("target is > " + a);
        }
      }
    });
  } else {
    var mid = a + Math.floor((b-a)/2);
    check(name, mid, function(ok) {
      if (ok) {
        console.log("range: " + a + "\t<-|  \t" + b);
        track(name, a, mid, lastfail);
      } else {
        console.log("range: " + a + "\t  |->\t" + b);
        track(name, mid+1, b, mid);
      }
    });
  }
}