content: package v100;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
  
  public class SuperLongSums_UVa10013 {
  
  	
  	public static void main(String[] args) throws IOException {
  		Scanner sc = new Scanner(System.in);
  		PrintWriter out = new PrintWriter(System.out);
  
  		int tc = sc.nextInt();
  		while(tc-->0)
  		{
  			int m = sc.nextInt();
  			int[] a = new int[m], b = new int[m];
  			for(int i = 0; i < m; ++i)
  			{
  				a[m - i - 1] = sc.nextInt();
  				b[m - i - 1] = sc.nextInt();
  			}
  			StringBuilder ans = new StringBuilder();
  			for(int i = 0, c = 0; i < m; ++i)
  			{
  				int s = a[i] + b[i] + c;
  				ans.append(s % 10);
  				c = s / 10;
  			}
  			out.println(ans.reverse());
  			if(tc != 0)
  				out.println();
  		}
  		out.flush();
  		out.close();
  	}
  
  	static class Scanner 
  	{
  		StringTokenizer st;
  		BufferedReader br;
  
  		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}
  
  		public String next() throws IOException 
  		{
  			while (st == null || !st.hasMoreTokens()) 
  				st = new StringTokenizer(br.readLine());
  			return st.nextToken();
  		}
  
  		public int nextInt() throws IOException {return Integer.parseInt(next());}
  
  		public long nextLong() throws IOException {return Long.parseLong(next());}
  
  		public String nextLine() throws IOException {return br.readLine();}
  
  		public double nextDouble() throws IOException { return Double.parseDouble(next()); }
  
  		public boolean ready() throws IOException {return br.ready();} 
  	}
  } 