# リストに整数を格納
x = [int(i) for i in input().split()]

# リストに1~10を格納
y = [i for i in range(1,11)]

for i in range(len(x)):
	if x[i] != y[i]:
		print(y[i])
		break;
	if i == len(x) -1:
		print(y[i+1])