N = int(input())

A = list(map(int, input().split()))

Ai = [0] * N

for i in range(N):
    
    Ai[A[i] - 1] = i
    
ans = 0

for i in range(N - 1):
    
    if Ai[i] > Ai[i + 1]:
        
        ans = i + 1
        
print(ans)