import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

x,y,d = map(int,read().split())

x_min = max(0, d-y)
x_max = min(x, d)

answer = x_max - x_min + 1
if answer < 0:
    answer = 0
print(answer)