n = int(input())
a = list(map(int,input().split()))
s = 0
if a[n - 1] == n:
    s += 1;
t = a[n - 1]
f = True
for i in range(n - 2,-1,-1):
    if a[i] == 1:
        f = True
    if a[i] + 1 == t:
        s += 1
        t = a[i]
        f = False
if f:
    s += 1
print(n - s)