Polycarpus adores TV series. Right now he is ready to finish watching a season of a popular sitcom "Graph Theory". In total, the season has n episodes, numbered with integers from 1 to n.

Polycarpus watches episodes not one by one but in a random order. He has already watched all the episodes except for one. Which episode has Polycaprus forgotten to watch?


-----Input-----

The first line of the input contains integer n (2 ≤ n ≤ 100000) — the number of episodes in a season. Assume that the episodes are numbered by integers from 1 to n.

The second line contains n - 1 integer a_1, a_2, ..., a_{n} (1 ≤ a_{i} ≤ n) — the numbers of episodes that Polycarpus has watched. All values of a_{i} are distinct.


-----Output-----

Print the number of the episode that Polycarpus hasn't watched.


-----Examples-----
Input
10
3 8 10 1 7 9 6 5 2

Output
4

Difficulty: interview

Starter code:

Solutions:
"""
Codeforces Testing Round 10 Problem A

Author  : chaotic_iak
Language: Python 3.3.4
"""

def read(mode=2):
    # 0: String
    # 1: List of strings
    # 2: List of integers
    inputs = input().strip()
    if mode == 0:
        return inputs
    if mode == 1:
        return inputs.split()
    if mode == 2:
        return [int(x) for x in inputs.split()]

def write(s="\n"):
    if isinstance(s, list): s = " ".join(s)
    s = str(s)
    print(s, end="")

################################################### SOLUTION
n, = read()
a = read()
write(n*(n+1)//2 - sum(a))

print(next(iter(set(range(1, int(input()) + 1)) - set(map(int, str.split(input()))))))


n=int(input())

L=list(map(int,input().split()))
Taken=[False]*n
for item in L:
    Taken[item-1]=True
for i in range(n):
    if(not Taken[i]):
        print(i+1)
        break


n = int(input())
a = set(input().split())
b = set()
for i in range(1, n + 1):
    b.add(str(i))
for i in b.difference(a):
    print(i)

n=int(input())
ser={ i for i in range(1,1+n)}
smotr=set(map(int, input().split()))
for i in ser:
    if i not in smotr:
        print(i)
        break


n=int(input())
series=list(map(int,input().split()))
smotrel=[False]*100000
for i in series:
    smotrel[i-1]=True
for i in range(n):
    if not smotrel[i]:
        break
print(i+1)


n = int(input())
sum = n * (n + 1) // 2
for x in map(int, input().split()):
	sum -= x

print(sum)


n = int(input())
num = list(map(int, input().split()))

tot1 = 0
tot2 = 0

for i in range(n):
    tot1 += (i+1)

for i in range(n-1):
    tot2 += num[i]
miss = tot1 - tot2
print(miss)


n=int(input())
a=input().split()
s=n*(n+1)//2
for i in range(n-1):
	s-=int(a[i])
print(s)


n = int(input())
a = set(map(int, input().split()))
print(list(set(range(1, n+1))-a)[0])


n=int(input())
print((n*n+n)//2-sum(list(map(int,input().split()))))


i=input;n=int(i());print((n*n+n)//2-sum(map(int,i().split())))


i,z=input,int;n=z(i());print((n*n+n)//2-sum(map(z,i().split())))


i,z=input,int
n=z(i())
print((n*n+n)//2-sum(map(z,i().split())))


n = int(input())
ser = {x for x in range(1, n+1)}
serw = {int(x) for x in input().split()}
print(list(ser - serw)[0])


n = int(input())

x = set(map(int, input().split(" ")))

for i in range(1,n+1):
    if i not in x:
        print(i)

print((set(range(1, int(input()) + 1)) - set(map(int, input().split()))).pop())


print(((2 * int(input()) + 1) ** 2 - 1) // 8 - sum(map(int, input().split())))


n = int(input())
s = n * (n + 1) / 2
a = list(map(int, input().split()))
print(int(s - sum(a)))

n = int(input())
l = list(map(int, input().split()))
ris = 0
for e in l:
    ris += e
print(int((n*(n+1)/2)-ris))

n = int(input())
s = sum([int(i) for i in input().split()])
print(n * (n + 1) // 2 - s)

n = int(input())
series = set(map(int, input().split()))

print(*(set(range(1, n+1)) - series))

n = int(input())
watched = [False]*n
for i in map(int, input().split()):
    watched[i-1] = True

for i in range(n):
    if not watched[i]:
        print(i+1)
        break

#!/usr/bin/env python3

total_episodes = int(input())
watched_episodes = list(map(int, input().split()))
total_sum = total_episodes * (total_episodes + 1) // 2
watched_sum = sum(watched_episodes)
print(total_sum - watched_sum)