#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

typedef long long ll;
const int inf = 1000000000;

int main()
{
    int T;
    scanf("%d", &T);
    for (int t = 1; t <= T; t++) {
        int K;
        scanf("%d", &K);
        int maxz = -inf;
        int mink = inf;
        int minh = inf;
        for (int i = 0; i < K; i++) {
            int a, b;
            scanf("%d%d", &a, &b);
            maxz = max(maxz, a+i);
            mink = min(mink, b-i);
            minh = min(minh, b-(maxz-i));
            minh = min(minh, mink+i-a);
        }
        printf("K prechodu reky je treba %d pontonu.\n",minh);
    }

    return 0;
}