#include <bits/stdc++.h>

using namespace std;

int t, n;
pair<int, int> x[1005];

int main() {
    scanf("%d", &t);
    while (t--) {
        int ta, tb, ans = 0;
        scanf("%d", &n);
        scanf("%d%d", &ta, &tb);
        for (int i = 1; i < n; i++) {
            int tc, td;
            scanf("%d%d", &tc, &td);
            if (max(ta, tc) <= min(tb, td)) {
                ta = max(ta, tc);
                tb = min(tb, td);
            } else if (tb < tc) {
                int tmp = (tc - tb + 1) / 2;
                ans += tmp;
                tb += tmp * 2;
                ta = max(tb - 1, tc);
                tb = min(tb, td);
            } else {
                int tmp = (ta - td + 1) / 2;
                ans += tmp;
                ta -= tmp * 2;
                tb = min(ta + 1, td);
                ta = max(ta, tc);
            }
        }
        printf("%d\n", ans);
    }
}