import strutils, sequtils, algorithm, math


var
  xyd = split(readLine(stdin), ' ').map(parseInt)
  result : int

if xyd[0] + xyd[1] < xyd[2]:
  result = 0
elif max(xyd[0], xyd[1]) < xyd[2]:
  result = xyd[0] + xyd[1] - xyd[2] + 1
else:
  result = min(xyd[0], xyd[1], xyd[2]) + 1

echo(result)