import sequtils, strutils

let
  a, b, cd = stdin.readLine.split.map parseInt
  aw = a[0]
  ab = a[1]
  bw = b[0]
  c = cd[0]
  d = cd[1]
var
  x = 0
  y: int

if c > ab:
  x = c - ab

y = min(d, bw + x)

echo aw - x + y