#include<iostream>

#include<string.h>

#include<algorithm>

#include<stdio.h>

#include<vector>

#define pii pair<int,int>

#define pb push_back

#define mp make_pair

#define LL long long

using namespace std;

vector<pii>v;

const int maxx = ;

int a[maxx];

int b[maxx];

int n;

LL go(int x){

   LL ans=;

   for(int i=;i<v.size();i++){

      if (v[i].first>x){

          ans+=(v[i].first-x+)/;

          if (i<v.size()-){

             if ((v[i].first-x)%){ ///长度为奇数

                 if (v[i+].first>v[i].second && v[i].second-v[i].first>){

                    x=v[i].first+;

                 }else x=v[i].first;

             }else x=v[i].first;

          }else x=v[i].first;

      }else {

          ans+=(x-v[i].second+)/;

          if (i<v.size()-){

              if ((x-v[i].second)%){

                 if(v[i+].second<v[i].first && v[i].second-v[i].first>){

                    x=v[i].second-;

                 }else x=v[i].second;

              }else x=v[i].second;

          }else x=v[i].second;

      }

   }

   return ans;

}

int main(){

  int t;

  scanf("%d",&t);

  while(t--){

    v.clear();

    scanf("%d",&n);

    scanf("%d%d",&a[],&b[]);

    int l=a[],r=b[];

    for (int i=;i<=n;i++){

        scanf("%d%d",&a[i],&b[i]);

        if (a[i]<=r && b[i]>=l){

            l=max(l,a[i]);

            r=min(r,b[i]);

        }else {

            v.pb(mp(l,r));

            l=a[i];

            r=b[i];

        }

    }

    v.pb(mp(l,r));

    LL ans=2e18;

    ans=min(ans,go(v[].first));

    ans=min(ans,go(v[].second));

    printf("%lld\n",ans);

  }

  return ;

}