/*
 * =template=.cpp
 * Copyright (C) 2017 hzw <hzw@huzhenweideMacBook.local>
 *
 * Distributed under terms of the MIT license.
 */
#include<cstdio>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<set>
#include<map>
#include<queue>
#include<string>
#include<cstring>
#include<cstdlib>
#include<cassert>
#include<unordered_map>
#define FR first
#define SC second
#define MP make_pair
#define rep(i,a,b) for (int i=a;i<=b;i++)
#define pb push_back
#define ws wss
#define left lll
#define right rrr
using namespace std;
typedef long long LL;
typedef pair<int,int> PII;
template<class T> void upmax(T &a,T b) { if (a<b) a=b;}
template<class T> void upmin(T &a,T b) { if (a>b) a=b;}
void read(int &x)
{
    char ch;int fu=1;
    while ((ch=getchar())<=32);
    x=0;
    if (ch=='-') fu=-1;else x=ch-48;
    while ((ch=getchar())>32) x=x*10+ch-48;
    x*=fu;
}
void read(unsigned long long &x)
{
    char ch;int fu=1;
    while ((ch=getchar())<=32);
    x=0;
    if (ch=='-') fu=-1;else x=ch-48;
    while ((ch=getchar())>32) x=x*10+ch-48;
    x*=fu;
}
const double pi=acos(-1);
void upmax(int &a,int b) { if (a<b) a=b;}
void upmin(int &a,int b) { if (a>b) a=b;}
//-----------------------

int exp(int a,int b,int c)
{
    int d=1;
    while (b)
    {
        if (b&1) d=1LL*d*a%c;
        b>>=1;a=1LL*a*a%c;
    }
    return d;
}
int gcd(int a,int b) { return b>0?gcd(b,a%b):a;}
const int N=110000,p=1000000007;
int cas,n;
int main()
{
    scanf("%d",&cas);
    while (cas--)
    {
        scanf("%d",&n);
        int l,r;
        int cost=0;
        scanf("%d%d",&l,&r);
        for (int i=2;i<=n;i++)
        {
            int a,b;
            scanf("%d%d",&a,&b);
            if (r<=a) 
            {
                cost+=(a-r+1)/2;
                l=a;
                if ((a-r)%2==1&&a<b) r=a+1;else r=a;
            }
            else
            if (l>=b) 
            {
                cost+=(l-b+1)/2;
                r=b;
                if ((l-b)%2==1&&a<b) l=b-1;else l=b;
            }
            else
            {
                l=max(l,a);
                r=min(r,b);
            }
        }
        printf("%d\n",cost);
    }
}