/*
* @Author: ISSAC
* @Date:   2022-07-29
* @File:   K.cpp
* @Last Modified time: 2022-07-29
*/
#include <bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
typedef long long i64;
typedef pair<int,int> PII;
mt19937 rnd();
const int mod = 1e9 + 7;

const int P = 998244353;
int norm(int x) {
    if (x < 0) {
        x += P;
    }
    if (x >= P) {
        x -= P;
    }
    return x;
}
template<class T>
T power(T a, i64 b) {
    T res = 1;
    for (; b; b /= 2, a *= a) {
        if (b % 2) res *= a;
    }
    return res;
}

struct Z {
    int x;
    Z(int x = 0) : x(norm(x)) {}
    Z(i64 x) : x(norm(x % P)) {}
    int val() const {
        return x;
    }
    Z operator-() const {
        return Z(norm(P - x));
    }
    Z inv() const {
        assert(x != 0);
        return power(*this, P - 2);
    }
    Z &operator*=(const Z &rhs) {
        x = i64(x) * rhs.x % P;
        return *this;
    }
    Z &operator+=(const Z &rhs) {
        x = norm(x + rhs.x);
        return *this;
    }
    Z &operator-=(const Z &rhs) {
        x = norm(x - rhs.x);
        return *this;
    }
    Z &operator/=(const Z &rhs) {
        return *this *= rhs.inv();
    }
    friend Z operator*(const Z &lhs, const Z &rhs) {
        Z res = lhs;
        res *= rhs;
        return res;
    }
    friend Z operator+(const Z &lhs, const Z &rhs) {
        Z res = lhs;
        res += rhs;
        return res;
    }
    friend Z operator-(const Z &lhs, const Z &rhs) {
        Z res = lhs;
        res -= rhs;
        return res;
    }
    friend Z operator/(const Z &lhs, const Z &rhs) {
        Z res = lhs;
        res /= rhs;
        return res;
    }
    friend std::istream &operator>>(std::istream &is, Z &a) {
        i64 v;
        is >> v;
        a = Z(v);
        return is;
    }
};

void solve(){
	int n, m; cin >> n >> m;
	Z a = Z(n - m) / Z(2);
	cout << a.val() << "\n";
}

signed main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr); 
    int _; cin >> _;
    while(_ --){
    	solve();
    }
    return 0;
}