x,y,d=map(int,input().split())
if x>=d and y>=d:
  print(d+1)
elif x<d and y>=d:
  print(x+1)
elif x>=d and y<d:
  print(y+1)
else:
  ans=x+y+1-d
  if ans>=0:
    print(ans)
  else:
    print(0)