C :

#include<stdio.h>
int main()
{
	int T,N,i,n[50],sum1,sum2;
	scanf("%d",&T);
	while(T--)
	{
		sum1=sum2=0;

		scanf("%d",&N);
		
		for(i=1;i<N+1;i++)
			sum1+=i;

		for(i=0;i<N-1;i++)
		{
			scanf("%d",&n[i]);
			sum2+=n[i];
		}
		printf("%d\n",sum1-sum2);
		
	}


	return 0;

}

C++ :

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>

using namespace std;
#define maxn 1000 + 6
int six[maxn];

int main()
{
    int i,j,k;
    int t,n,m;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        memset(six,0,maxn);
        for(i=1;i<n;i++)
        {
            scanf("%d",&m);
            six[m]=1;
        }
        for(i=1;i<=n;i++)
        {
            if(six[i]==0)
                break;
        }
        printf("%d\n",i);
    }
    return 0;
}

Pascal :

var
 t,n,i,j:longint;
 a:array[1..50]of longint;
 b:array[0..50]of boolean;
begin
 readln(t);
 for i:=1 to t do
  begin
   readln(n);
   for j:=1 to 50 do
    begin
     a[j]:=0;
     b[j]:=true;
    end;
   for j:=1 to n-1 do
    read(a[j]);
   for j:=1 to n do
    b[a[j]]:=false;
   for j:=1 to n do
    if b[j] then writeln(j);
  end;
end.

Java :

import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int T = sc.nextInt();
		for(int i=0;i<T;i++){
			int N = sc.nextInt();
			int[] arr ;
			int[] r;
			arr = new int[N] ;
			r = new int[N] ;
			for(int j=0;j<r.length;j++){
				r[j] = j+1;
			}
			arr[N-1]=51;
			for(int k=0;k<arr.length-1;k++){
				arr[k] = sc.nextInt();
			}
			int temp = 0;
			for(int  m = 0;m<arr.length-1;m++){
				for(int mm=0;mm<arr.length-1-m;mm++){
					if(arr[mm]>arr[mm+1]){
						temp = arr[mm];
						arr[mm]= arr[mm+1];
						arr[mm+1]=temp;
					}
				}
			}
			
			for(int o=0;o<N;o++){
				int ans;
				ans = r[o]-arr[o];
				if(ans!=0){
					System.out.println(r[o]);
					o=100;
				}
			}
			
		}
	}
}