#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;

typedef long long ll;

const int N = 1e3 + 100;

struct node {
    int l, r;
}sa[N];

int n;



void solve() {
    int l = -1e9, r = 1e9, st;
    for (int i = 1; i <= n; i++) {
        if (r < sa[i].l) {
            st = r;
            break;
        }
        if (l > sa[i].r) {
            st = l;
            break;
        }
        l = max(l, sa[i].l);
        r = min(r, sa[i].r);
    }
    ll ans = 0;
    l = st, r = st;
    for (int i = 1; i <= n; i++) {
        if (r < sa[i].l) {
            int d = sa[i].l - r;
            int t = d / 2;
            if (d % 2) t++;
            ans += t;
            l = r + t * 2 - 1;
            r = r + t * 2;
            l = max(l, sa[i].l);
            r = min(r, sa[i].r);
        }
        else if (l > sa[i].r) {
            int d = l - sa[i].r;
            int t = d / 2;
            if (d % 2) t++;
            ans += t;
            r = l - 2 * t + 1;
            l = l - 2 * t;
            l = max(l, sa[i].l);
            r = min(r, sa[i].r);
        }
        else {
            l = max(l, sa[i].l);
            r = min(r, sa[i].r);
        }
    }
    printf("%lld\n", ans);
}

int main() {
    int T;
    scanf("%d", &T);
    while (T--) {
        scanf("%d", &n);
        for (int i = 1; i <= n; i++) scanf("%d%d", &sa[i].l, &sa[i].r);
        solve();
    }
    return 0;
}