// yukicoder: No.126 2基のエレベータ
// 2019.4.12 bal4u

#include <stdio.h>

#define ABS(a)  ((a)>=0?(a):-(a))

int main()
{
	int A, B, S, a, b, ans;
	scanf("%d%d%d", &A, &B, &S);
	a = ABS(A - S), b = ABS(B - S);
	if (S == 1) ans = a + 1;
	else if (a <= b) ans = a + S;
	else {
		if (S > A) {
			if (A == 0) ans = b + S + 1;
			else ans = b + S;
		}
		else if (a < S - 1) ans = a + b + A;
		else ans = A + b + S - 1;
	}
	printf("%d\n", ans);
	return 0;
}