import strutils

var
  sa, sb: string
  pa, pb: string
  xa, xb: string
  res:string = nil

proc conv(ch:char): int = result = ch.int - '0'.int
  
var scan = stdin.readLine.split
sa = scan[0]
pa = scan[1]
scan = stdin.readLine.split
sb = scan[0]
pb = scan[1]

if pa.len < pb.len: res = sb
elif pa.len > pb.len: res = sa
else:
  for i in 0.. <pa.len:
    var
      x = conv(pa[i])
      y = conv(pb[i])
    if x < y:
      res = sb
      break
    elif x > y:
      res = sa
      break
if res == nil: res = "-1"
echo res