N=int(input())
a=[int(i) for i in input().split() ]

pos=[None for i in range(N+1)]
for i in range(N):
    pos[a[i]]=i

asc_min=N
for i in reversed(range(1,N)):
    i_pos = pos[i]
    asc=True
    for j in range(i+1,N+1):
        if pos[j]<i_pos:
            asc=False
            break
    if asc==True:
        asc_min=i
    else:
        break

print(asc_min-1)