#include <bits/stdc++.h>
using namespace std;
inline long long read() {
  long long x = 0, f = 1;
  char c = getchar();
  while (c != '-' && (c < '0' || c > '9')) c = getchar();
  if (c == '-') f = -1, c = getchar();
  while (c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
  return f * x;
}
const long long N = 2e5 + 7;
const long long M = 5e4 + 7;
const long long MAXN = 4e18 + 7;
const long long Mod = 1e9 + 7;
long long _, i, j, k, n, m, p, s, T, l, r, o, u, v, w, x, y, z, st, en, sx, sy,
    ans, th, ma, mi, mod, sum, num, len, res, flag, cas, ret, mid, cnt, now,
    nex, tmp;
long long c[N];
char ch;
queue<long long> q;
vector<long long> g[N];
string s1, s2, s3;
struct node {
  long long l, r;
} a[N];
bool cmp(node a, node b) {
  long long x1 = min(abs(a.l - x), abs(a.r - x));
  long long x2 = min(abs(b.l - x), abs(b.r - x));
  return x1 < x2;
}
signed main() {
  ios::sync_with_stdio(false);
  long long T = 1;
  double x1, x2, x3, y1, y2, y3, z1, z2, z3;
  cin >> T;
  while (T--) {
    cin >> n >> x >> m;
    l = r = x;
    cnt = 0;
    for (i = 1; i <= m; i++) {
      cin >> a[i].l >> a[i].r;
      if (a[i].l <= l && r <= a[i].r) l = a[i].l, r = a[i].r;
      if (l <= a[i].l && a[i].l <= r) r = max(r, a[i].r);
      if (l <= a[i].r && a[i].r <= r) l = min(l, a[i].l);
    }
    cout << r - l + 1 << endl;
  }
  return 0;
}
