#include<iostream>
#include<vector>
#include<set>
#include<map>
#include<cmath>
#include<algorithm>
using namespace std;

int main() {
  ios::sync_with_stdio(false);
  int N; cin >> N;
  while (N--) {
    long K; cin >> K;

    long A, B;
    cin >> A >> B;

    long lineLx = A, lineRx = B;
    long Lmin = B - A, Rmin = B - A;
    for (int y = 1; y < K; ++y) {
      cin >> A >> B;
      lineLx -= 1;
      lineRx += 1;

      lineLx = max(lineLx, A);
      lineRx = min(lineRx, B);

      Lmin = min(Lmin, lineRx - lineLx);
      Rmin = min(Rmin, lineRx - lineLx);
    }
    cout << "K prechodu reky je potreba " << min(Lmin, Rmin) << " pontonu." << endl;
  }
  return 0;
}