#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int Mod=1e9+7;
const ll INF = 10000000000000;
const int N = 1e6+7;
 
    void solve() {
       int n,m,x;
       cin >> n >> x >> m;
       int mi = x, ma = x;
       while(m--){
        int a,b;cin >> a >> b;
        if(mi<=b ){
           mi=min(a,mi);
           ma=max(b,ma);
        }
       }
       cout << ma-mi+1 << '\n';
    }
int main(){ 
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int t;
    cin >> t;
    while (t--) solve();
 
    return 0;
}

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