线段树（离散化+区间覆盖）

//#include<bits/stdc++.h>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <string>
#include <stdio.h>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <string.h>
#include <vector>
typedef long long ll ;
#define int ll
#define mod 1000000007
#define gcd __gcd
#define rep(i , j , n) for(int i = j ; i <= n ; i++)
#define red(i , n , j)  for(int i = n ; i >= j ; i--)
#define ME(x , y) memset(x , y , sizeof(x))
//ll lcm(ll a , ll b){return a*b/gcd(a,b);}
ll quickpow(ll a , ll b){ll ans=1;while(b){if(b&1)ans=ans*a%mod;b>>=1,a=a*a%mod;}return ans;}
//int euler1(int x){int ans=x;for(int i=2;i*i<=x;i++)if(x%i==0){ans-=ans/i;while(x%i==0)x/=i;}if(x>1)ans-=ans/x;return ans;}
//const int N = 1e7+9; int vis[n],prime[n],phi[N];int euler2(int n){ME(vis,true);int len=1;rep(i,2,n){if(vis[i]){prime[len++]=i,phi[i]=i-1;}for(int j=1;j<len&&prime[j]*i<=n;j++){vis[i*prime[j]]=0;if(i%prime[j]==0){phi[i*prime[j]]=phi[i]*prime[j];break;}else{phi[i*prime[j]]=phi[i]*phi[prime[j]];}}}return len}
#define SC scanf
#define INF  0x3f3f3f3f
#define PI acos(-1)
#define pii pair<int,int>
#define fi first
#define se second
#define lson l,mid,root<<1
#define rson mid+1,r,root<<1|1
using namespace std;
const int N = 1e6+100;
const int maxn = 1e4+9;
int n , m , li[maxn] , ri[maxn];
int b[maxn<<3], len , tree[maxn<<4] , ans ;
int vis[maxn];

void init(){
    ME(tree , -1);
    ME(vis , 0);
    len = 0 ;
    ans = 0 ;
}
void pushdown(int root){
    tree[root<<1] = tree[root<<1|1] = tree[root];
    tree[root] = -1 ;
}

void update(int L , int R , int l , int r , int root , int color){
    if(l >= L && r <= R){
        tree[root] = color;
        return ;
    }
    if(tree[root] != -1)pushdown(root);
    int mid = (l + r) >> 1 ;
    if(mid >= L) update(L , R , lson , color);
    if(mid < R) update(L , R , rson , color);
}

void query(int l , int r , int root){
    if(l == r){
        if(tree[root] != -1){
            if(!vis[tree[root]]){
                ans++;
            }
            vis[tree[root]] = 1 ;
        }
        return ;
    }
    if(tree[root] != -1) pushdown(root);
    int mid = (l + r) >> 1 ;
    query(lson);
    query(rson);
}

void solve(){
    init();
    int n ;
    scanf("%lld" , &n);
    rep(i , 1 , n){
        scanf("%lld%lld" , &li[i] , &ri[i]);
        b[++len] = li[i];
        b[++len] = ri[i];
    }
    sort(b + 1 , b + 1 + len);
    len = unique(b + 1 , b + 1 + len) - b - 1 ;//离散化
    red(i , len , 2){
        if(b[i] - b[i-1] > 1) b[++len] = b[i] - 1 ;//相差大于2则插入一个中间值
    }
    sort(b + 1 , b + 1 + len);
    rep(i , 1 , n){
        int l = lower_bound(b + 1 , b + 1 + len , li[i]) - b ;
        int r = lower_bound(b + 1 , b + 1 + len , ri[i]) - b ;
        update(l , r , 1 , len , 1 , i);
    }
    query(1 , len , 1);
    cout << ans << endl;
}

signed main()
{
    //ios::sync_with_stdio(false);
    //cin.tie(0); cout.tie(0);
    int t ;
    scanf("%lld" , &t);
    while(t--){
        solve();
    }
}