Codeforces 1018D D. Order book

#include<iostream>
#include<cstdio> 
#include<cmath>
#include<queue>
#include<vector>
#include<string.h>
#include<cstring>
#include<algorithm>
#include<set>
#include<map>
#include<fstream>
#include<cstdlib>
#include<ctime>
#include<list>
#include<climits>
#include<bitset>
using namespace std;
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fopen freopen("input.in", "r", stdin);freopen("output.in", "w", stdout);
#define left asfdasdasdfasdfsdfasfsdfasfdas1
#define tan asfdasdasdfasdfasfdfasfsdfasfdas
typedef long long ll;
typedef unsigned int un;
const int desll[4][2]={{0,1},{0,-1},{1,0},{-1,0}};
const ll mod=1e9+7;
const int maxn=4e5+7;
const int maxm=1e6+7;
const double eps=1e-4;
int m,n;
int ar[maxn];
set<int> se;
char ch[100];
int maxx=308983067;

int main()
{
    scanf("%d",&n);
    int ans=1;
    int l=0,r=maxx;
    bool ma=true;
    int ins=0;
    for(int i=0;i<n;i++){
        int x;
        scanf("%s",ch);
        scanf("%d",&x);
        if(ch[1]==‘D‘){
            if(se.count(x)==0 && l<x && x<r){
                se.insert(x);
                ins++;
            }
            else if(se.count(x)==1){
                ma=0;
            }
            else{
                se.insert(x);
            }
        }
        else{
            if(se.count(x)==1 && x<=r && x>=l){
                if(x!=l&&x!=r)ans = ans*2%mod;
                set<int>::iterator iter=se.find(x);
                if(iter==se.begin())l=0;
                else{
                    iter--;
                    l=*iter;
                    iter++;
                }
                se.erase(iter++);
                if(iter==se.end())r=maxx;
                else{
                    r=*iter;
                }
            }
            else{
                ma=0;
            }
            ins=0;
        }
    }
    if(ins){
        ans = 1LL*ans*(ins+1)%mod;
    }
    if(ma)printf("%d\n",ans);
    else printf("0\n");

    return 0;
}