原题链接：

• http://codeforces.com/problemset/problem/835/E
• https://www.luogu.com.cn/problem/CF835E

题解：

• https://www.luogu.com.cn/problem/solution/CF835E

附赠一个自测的小工具：

#include <iostream>
#include <algorithm>

using namespace std;
int c, p[1005];
int main()
{
	int n,x,y,p1,p2; 
    cin>>n>>x>>y>>p1>>p2;
    cout << n << " " << x << " " << y << endl;
    int cnt = 0;
    bool flag = true;
    while (1)
    {
    	char op;
    	cin>>op;
        if (op == '!')
        {
        	int pp1,pp2; 
            cin>>pp1>>pp2; 
			if (pp1 == p1 && pp2 == p2)
                cout<<"Good"<<endl;
            else
            	cout<<"WA"<<endl;
        }
        if (op == '?')
        {
            cnt++;
            if (cnt > 19)
                cout<<"Too Many '?'"<<endl;
            cin>>c;
            for (int i = 1; i <= c; i++)
                cin>>p[i];
            sort(p + 1, p + c + 1);
            int res = 0;
            for (int i = 1; i <= c; i++)
            {
                if (p[i] == p1 || p[i] == p2)
                    res = res ^ y;
                else
                    res = res ^ x;
                if (i > 1 && p[i] == p[i - 1])
                    cout<<"Same P[i]"<<endl;
            }
            cout << res << endl;
        }
    }
}