#include<bits/stdc++.h>

using namespace std;

struct data
{
    int a,b;

} arr[1000005];

int ans[1000005];

int main()
{
    ios_base::sync_with_stdio(0);

    cin.tie(0);


    long long n,m,i,j,k,carry,tag=0;

    cin>>n;

    for(i=1; i<=n; i++)
    {
        if(tag)cout<<"\n";
        tag=1;

        cin>>m;

        for(j=1; j<=m; j++)
            cin>>arr[j].a>>arr[j].b;

        carry = 0;
        k = 0;

        for(j=m; j>=1; j--)
        {
            if(carry+arr[j].a+arr[j].b>9)
            {
                ans[++k] = (carry+arr[j].a+arr[j].b)%10;
                carry = (carry+arr[j].a+arr[j].b)/10;
            }
            else
            {
                ans[++k] = carry+arr[j].a+arr[j].b;

                carry = 0;
            }
        }

        if(carry)ans[++k]=carry;

        for(j=k; j>=1; j--)
            cout<<ans[j];
        cout<<"\n";

    }

    return 0;
}