b.cpp

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
template <typename T1, typename T2>
ostream &operator <<(ostream &os, pair<T1, T2> p){os << p.first << " " << p.second; return os;}
template <typename T>
ostream &operator <<(ostream &os, vector<T> &v){for(T i : v)os << i << ", "; return os;}
template <typename T>
ostream &operator <<(ostream &os, set<T> s){for(T i : s) os << i << ", "; return os;}
template <typename T1, typename T2>
ostream &operator <<(ostream &os, map<T1, T2> m){for(pair<T1, T2> i : m) os << i << endl; return os;}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int t; cin >> t;
    while(t--){
        int n, x, m; cin >> n >> x >> m;
        int l = x, r = x;
        for(int i = 0; i < m; i++){
            int a, b; cin >> a >> b;
            if((l <= b && l >= a)){
                l = a;
            }
            if(r <= b && r >= a){
                r = b;
            }
        }
        cout << r - l + 1 << endl;
    }
    return 0;
}