#include <bits/stdc++.h>
using namespace std;
int dy4[4] = {-1, 0, +1, 0};
int dx4[4] = {0, +1, 0, -1};
int dy8[8] = {-1, -1, 0, 1, 1, 1, 0, -1};
int dx8[8] = {0, 1, 1, 1, 0, -1, -1, -1};
const long long INF = 1LL << 60;
const long long MOD = 1e9 + 7;
bool greaterSecond(const pair<int, int>& f, const pair<int, int>& s) {
  return f.second > s.second;
}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
long long conbinationMemo[100][100];
void cmemoInit() {
  for (int i = 0; i < (int)(100); i++) {
    for (int j = 0; j < (int)(100); j++) {
      conbinationMemo[i][j] = -1;
    }
  }
}
long long nCr(long long n, long long r) {
  if (conbinationMemo[n][r] != -1) return conbinationMemo[n][r];
  if (r == 0 || r == n) {
    return 1;
  } else if (r == 1) {
    return n;
  }
  return conbinationMemo[n][r] = (nCr(n - 1, r) + nCr(n - 1, r - 1));
}
long long nPr(long long n, long long r) {
  r = n - r;
  long long ret = 1;
  for (long long i = n; i >= r + 1; i--) ret *= i;
  return ret;
}
int main(void) {
  long long t;
  cin >> t;
  for (int ii = 0; ii < (int)(t); ii++) {
    long long n, m, x;
    cin >> n >> x >> m;
    long long nowr = x;
    long long nowl = x;
    for (int i = 0; i < (int)(m); i++) {
      long long l, r;
      cin >> l >> r;
      if (nowr < l || nowl > r) continue;
      nowr = max(nowr, r);
      nowl = min(nowl, l);
    }
    cout << nowr - nowl + 1 << endl;
  }
}
