import strutils, sequtils, algorithm, math
import parseutils

var
  aIn = readLine(stdin).split
  bIn = readLine(stdin).split
  a:tuple[name:string, point:string]
  b:tuple[name:string, point:string]

a =  (aIn[0], aIn[1])
b =  (bIn[0], bIn[1])

if a.point == b.point:
  echo -1
elif max(len(a.point), len(b.point)) == len(a.point):
  echo a.name
else:
  echo b.name