x,y,d = [int(i) for i in input().split()]
if d > x+y:
    print(0)
elif d == 0:
    print(1)
elif d > x or d > y:
    if x > y:
        print(x)
    else:
        print(y)
else:
    if x > y:
        print(x+1)
    else:
        print(y+1)