#!/usr/bin/env python


def read():
    return map(int, raw_input().split())


def work((A, B, S)):
    if S == 1:
        print abs(S - A) + 1
    elif abs(A - S) <= abs(B - S):
        print abs(A - S) + S
    elif B <= A:
        print abs(B - S) + min((abs(A - S) + 1) / 2 + A, A + S - 1)
    else:
        print abs(B - S) + min(abs(A - S) + A, A + S - 1)


if __name__ == "__main__":
    work(read())