#include <bits/stdc++.h>
using namespace std;
const long long N = pow(2, 32);
map<long long, long long> factorize(long long n) {
  map<long long, long long> ans;
  for (long long i = 2; i * i <= n; i++) {
    while (n % i == 0) {
      ans[i]++;
      n /= i;
    }
  }
  if (n > 1) {
    ans[n]++;
    n = 1;
  }
  return ans;
}
void FAST() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
long long binpow(long long a, long long b, long long m) {
  a %= m;
  long long res = 1;
  while (b > 0) {
    if (b & 1) res = res * a % m;
    a = a * a % m;
    b >>= 1;
  }
  return res;
}
long long answer(long long sum, vector<vector<long long>> a, long long n,
                 long long m) {
  long long cnt1 = 0, cnt0 = 0;
  for (long long i = 0; i < n; i++) {
    for (long long j = 0; j < m; j++) {
      if (i + j == sum || i + j == n + m - 2 - sum) {
        if (a[i][j])
          cnt1++;
        else
          cnt0++;
      }
    }
  }
  return min(cnt0, cnt1);
}
int main() {
  FAST();
  long long t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    long long x;
    cin >> x;
    long long m;
    cin >> m;
    long long l = x, r = x;
    long long tl, tr;
    bool act = 0;
    while (m--) {
      cin >> tl >> tr;
      if (!(tr < l || tl > r)) {
        l = min(l, tl);
        r = max(r, tr);
      }
    }
    cout << r - l + 1 << "\n";
  }
}
