#include <bits/stdc++.h>
using namespace std;
int t, n;
int main() {
    scanf("%d", &t);
    for (int tt = 0; tt < t; tt++) {
        scanf("%d", &n);
        int L = 1;
        int R = 1000000;
        int Z = 0;
        for (int i = 0; i < n; i++) {
            int a, b;
            scanf("%d%d", &a, &b);
            if (R < a) {
                if ((a - R) % 2 != 0 && (b - a) >= 1) {
                    Z += (a - R + 1) / 2;
                    L = a;
                    R = a + 1;
                } else {
                    Z += (a - R + 1) / 2;
                    L = R = a;
                }
            } else if (b < L) {
                if ((L - b) % 2 != 0 && (b - a) >= 1) {
                    Z += (L - b + 1) / 2;
                    L = b - 1;
                    R = b;
                } else {
                    Z += (L - b + 1) / 2;
                    L = R = b;
                }
            } else {
                L = max(L, a);
                R = min(R, b);
            }
        }
        printf("%d\n", Z);
    }
    return 0;
}