https://codeforces.com/contest/1101/problem/E

题解：思维

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q;
int ans,cnt,flag,temp;
char str;
int a,b,c,d;
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //scanf("%d",&n);
    //scanf("%d",&t);
    //while(t--){}
 char s[10];
    int x,y;
    scanf("%d",&n);
    for (int i=1;i<=n;++i)
    {
        scanf("%s%d%d",s,&x,&y);
        if (x>y) swap(x,y);
        if (s[0]=='+')
        {
            a=max(a,x);
            b=max(b,y);
        }
        else
        {
            if (a<=x&&b<=y) printf("YES\n");
            else printf("NO\n");
        }
    }

    //cout << "Hello world!" << endl;
    return 0;
}