#include<iostream>
#include<string>
#include<algorithm>
#include<cmath>
#include<vector>
#include<queue>
#include<stack>
#include<set>
#include<map>
#include<iomanip>
using namespace std;
typedef long long ll;
#define pb push_back
int main() {
    ios_base::sync_with_stdio(0); cin.tie(NULL);
    int t;
    cin >> t;
    while(t--) {
        ll n,k,total=0;
        cin >> n >> k;
        vector<ll> bags;
        for(ll i=1; i<k; i++) {
            bags.pb(i);
        }
        const int size = bags.size()/2;
        for(int i=0; i<size; i++) {
            for(int j=1; j<bags.size(); j++) {
                if(bags[0]+bags[j]==k){
                    total++;
                    bags.erase(bags.begin()+j);
                    bags.erase(bags.begin());
                    break;
                }          
            }
        }
        if(!bags.empty())total++;
        cout << total << endl;
    }
    return 0;
}