import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	X, Y, Z = getlist()
	if X + Z < Y or Y + Z < X:
		ans = min(X + Z, Y + Z)
		print(ans)
	else:
		ans = int((X + Y + Z) // 2)
		print(ans)


if __name__ == '__main__':
	main()