import strutils, sequtils

let
  Awb, Bwb, CD = stdin.readLine.split.map parseInt
  (C, D) = (CD[0], CD[1])

var
  A = (w: Awb[0], b: Awb[1])
  B = (w: Bwb[0], b: Bwb[1])

  Cw = max(0, C - A.b)

A.w -= Cw
B.w += Cw

A.w += min(D, B.w)

echo A.w