#include <iostream>

using namespace std;

int main(int argc, char **argv) {
    int tcount;
    cin >> tcount;

    for(int tcase=0; tcase<tcount; tcase++) {
        int length;
        cin >> length;
        int bestA = 0;
        int bestB = 1000000;

        int minimum = 1000000;

        for(int i=0; i<length; i++) {
            int a, b; cin >> a; cin >> b;

            if(a > bestA) {
                bestA = a;
            }
            if(b < bestB) {
                bestB = b;
            }

            int diff = bestB-bestA;
            if(diff < 0) {
                diff = 0;
            }

            if(diff < minimum) {
                minimum = diff;
            }

            bestA--;
            bestB++;
        }

        cout << "K prechodu reky je treba " << minimum << " pontonu." << endl;
    }

    return 0;
}