def main():
    x, y, d = map(int, input().split())

    if d <= min(x, y):
        print(d + 1)
    elif min(x, y) <= d <= max(x, y):
        print(min(x, y) + 1)
    elif max(x, y) <= d <= x + y:
        print(x + y - d + 1)
    else:
        print(0)


if __name__ == '__main__':
    main()