N = int(input())
A = list(map(int, input().split()))
gyaku = [-1]*(N + 1)

for i, a in enumerate(A):
    gyaku[a] = i

border = N + 1
ans = 0
for i in range(N, 0, -1): # 大きい数から配置
    if border < gyaku[i]:
        ans = i
        break
    border = min(border, gyaku[i])

print(ans)