#include<stdio.h>
#include<cmath>
#include<algorithm>
#include<iostream>
#include<queue>
#include<map>
using namespace std;


int a[1005];
int b[1005];
struct zjc {
    int cost, pos, finsh;
    bool operator < (const zjc & a) const
    {
        return cost > a.cost;
    }
};
int main() {
    int T;
    scanf("%d", &T);
    for (int tt = 0; tt < T; ++tt) {
        int n;
        scanf("%d", &n);
        for (int i = 0; i < n; ++i) {
            scanf("%d%d", &a[i], &b[i]);
        }
        for (int i = 1; i < n; ++i) {
            if (a[i]>=a[0] && a[i]<= b[0]) {
                a[0] = a[i];
            } else if (b[i]>=a[0] && b[i] <=b[0]) {
                b[0] = b[i];
            } else break;
        }
        zjc aa,bb;
        aa.cost = 0; aa.pos = a[0]; aa.finsh=1;
        bb.cost = 0; bb.pos = b[0]; bb.finsh=1;
        priority_queue<zjc> pp;
        pp.push(aa); pp.push(bb);
        map<pair<int,int>, int> mp;
        //mp[pair(0,a[0])] = 1;
        //mp[pair(0,a[0])] = 1;
        while(!pp.empty()) {
            zjc now = pp.top(); pp.pop();
           // cout << now.cost << " " << now.pos <<endl ;
            if (mp[make_pair(now.pos, now.finsh)]) continue;
            mp[make_pair(now.pos, now.finsh)] = 1;
            if (now.finsh == n) {
                printf("%d\n", now.cost);
                break;
            }
            zjc next = now; next.finsh++;
            int lll = a[now.finsh], rrr = b[now.finsh];
            int pos = now.pos;
            if (pos >= lll && pos <= rrr) {
                pp.push(next);
            } else if (pos < lll) {
                int dis = lll - pos;
                next.cost += (dis+1)/2;
                next.pos = lll;
                pp.push(next);
                if (dis%2 && rrr>lll) {
                    next.pos = lll+1;
                    pp.push(next);
                }
            } else if (pos > rrr) {
                int dis = pos -rrr;
                next.cost += (dis+1)/2;
                next.pos = rrr;
                pp.push(next);
                if (dis%2 && rrr > lll) {
                    next.pos = rrr -1;
                    pp.push(next);
                }
            }
        }
    }
    return 0;
}