听取WA声一片

#include<bits/stdc++.h>
using namespace std;

char ch;
int a,n,m;
stack<int> t;
bool house[50010];

int main()
{
	scanf("%d%d",&n,&m);
	for(int i=1;i<=m;i++)
	{
		cin>>ch;
		if(ch=='D')
		{
			scanf("%d",&a);
			house[a]=true;
			t.push(a);
		}
		if(ch=='R')
		{
			house[ t.top() ]=false;
			t.pop();
		}
		if(ch=='Q')
		{
			scanf("%d",&a);
			if(house[a])
			{
				printf("0\n");
				continue;
			}
			if(t.empty())
			{
				printf("%d\n",n);
				continue;
			}
			else
			{
				int ans=1;
				for(int i=a-1;a>=1;i--)
				{
					if(!house[i])
						ans++;
					else break;
				}
				for(int i=a+1;i<=n;i++)
				{
					if(!house[i])
						ans++;
					else break;
				}
				printf("%d\n",ans);
			}
		}
	}
	return 0;
}
/*
7 9 D 3 D 6 D 5 Q 4 Q 5 R Q 4 R Q 4
*/