#include <bits/stdc++.h>
using namespace std;
#define ll long long
int OO = 1000000;
ll mod = 1000000007;


int main() {
	ios::sync_with_stdio(0);
	//freopen("out.txt" , "w" , stdout);
	int t;
	cin>>t;
	while(t--){
		int n;
		cin>>n;
		int a[n],b[n];
		for (int i=0 ; i<n ; i++)cin>>a[i]>>b[i];
		int ans[n];
		for(int i=n-1 ; i>=0 ; i--){
			int temp = a[i]+b[i];
			if(i==0){
				ans[i]=temp;
			}else {
				ans[i]= temp%10;
				temp/=10;
				a[i-1]+=temp;
			}
		}
		for(int i=0 ;i<n ; i++)cout<<ans[i];
		cout<<endl;
		if(t!=0 )cout<<endl;
	}
}