N = int(input())
A = list(map(int, input().split())) 
l = 0
r = 0
cnt = 0
for i,a in enumerate(A,start=1):
    if l==0 and i!=a:
        l=i
    if r==0 and N<a:
        r=a
    if a<=N:
        cnt+=1
print(r-l-cnt)