#include<iostream>
#include<vector>
#include<cstdio>


int abs(int x) {
    if (x < 0)
        return -1*x;
    else
        return x;
}

int main() {
    int T;
    scanf("%d", &T);
    for (int t = 0; t < T; t++) {
        int dm = 1234567;
        int h;
        scanf("%d", &h);
        int re = 1000001, le = 0;
        for (int i = 0; i < h; i++) {

            int a,b;
            scanf("%d %d", &a, &b);
            //std::cout<<le << " " << re << " " << a << " " << b << " " << dm<<std::endl;
            if (i+a > le) {
                le = i+a;
            }
            if (b-i < re) {
                re = b-i;
            }
            if (dm > ((i+b)-le)) {
                dm = ((i+b)-le);
                //std::cout<<"p";
            }
            if (dm > (re-(a-i))) {
                dm = (re-(a-i));
                //std::cout <<"o";
            }

        }
        printf("K prechodu reky je treba %d pontonu.\n", dm);

    }


    return 0;
}