25400번: 제자리 ↗

import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
# sys.setrecursionlimit(10**7)

BLANK = " "

# inp = input
inp = lambda : sys.stdin.readline().rstrip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def gcd(a, b): return gcd(b, a % b) if b > 0 else a
def lcm(a, b): return a * b // gcd(a, b)


def solve():
    n = ii()
    l = mii()

    crt = 1
    cnt = 0

    for i in l:
        if i == crt:
            crt += 1
            cnt += 1
    

    p(n - cnt)


if __name__ == "__main__":
    tc = 1

    for t in range(1, tc+1):
        ret = solve()