You are given two positive integers, a and b (a<b ). For some positive integer n , two players will play a game starting with a pile of n stones. They take turns removing exactly a or exactly b stones from the pile. The player who is unable to make a move loses. Find a positive integer n such that the second player to move in this game has a winning strategy. This means that no matter what moves the first player makes, the second player can carefully choose their moves (possibly depending on the first player's moves) to ensure they win. 请帮我编写一个C++代码，并用中文解释

好的！下面是用C++编写的代码，并附有中文解释：

#include <iostream>

int main() {
    int t;
    std::cin >> t;  // 输入测试用例的数量

    while (t--) {
        int a, b;
        std::cin >> a >> b;  // 输入整数 a 和 b

        // 选择一个 n，使得在游戏开始时，第二个玩家有必胜策略
        int n = b - 1;  // 将 n 设置为 b-1
        std::cout << n << std::endl;  // 输出 n
    }

    return 0;
}

这段代码首先读取测试用例的数量 `t`，然后对于每个测试用例，它会读取整数 `a` 和 `b`。接下来，它将 `n` 设置为 `b-1`，这样第二个玩家就能够确保有必胜策略。最后，输出 `n`。

注意：问题中说明在给定的约束条件下，总是存在一个满足要求的正整数 `n`。以上代码选择了 `n` 的值为 `b-1`，但你也可以选择其他满足条件的正整数作为 `n`。