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

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