import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

b = list(map(int, read().split()))
for i in range(1, 10):
    if i != b[i - 1]:
        print(i)
        exit()
print(10)