#include <bits/stdc++.h>
using namespace std;

int main() {
    int t, n, c, d;
    scanf("%d", &t);
    while (t--) {
        scanf("%d", &n);
        set<int> cur;
        while (n--) {
            scanf("%d%d", &c, &d);
            int k = c + d;
            while (cur.count(k)) {
                cur.erase(k);
                k--;
            }
            cur.insert(k);
        }
        vector<int> v(cur.begin(), cur.end());
        if (v[0] < -1 || (v[0] == -1 && v.size() > 1 && v[1] == 0)) printf("NO\n");
        else printf("YES\n");
    }
}