#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n = 0;
	cin >> n;
	stack<int>arr;
	stack<int>brr;
	long long int xrr[150001];
	long long int crr[150001];
	char temp;
	int tp;
	int t = 0;
	while (n--)
	{
		cin >> temp;
		if (temp == 'I')
		{
			cin >> tp;
			arr.push(tp);
			if (t == 0)
			{ 
				xrr[++t] = tp; 
				crr[t] = tp;
			}
			else
			{
				xrr[++t] = xrr[t - 1] + tp;
				crr[t] = max(crr[t - 1], xrr[t]);
			}
		}
		else if (temp == 'D')
		{
			if (!arr.empty())
			{
				arr.pop();
				t--;
			}
		}
		else if (temp == 'L')
		{
			if (!arr.empty())
			{
				tp = arr.top();
				arr.pop();
				brr.push(tp);
				t--;
			}
		}
		else if (temp == 'R')
		{
			if (!brr.empty())
			{
				tp = brr.top();
				brr.pop();
				arr.push(tp);
				xrr[++t] = xrr[t - 1] + tp;
				crr[t] = max(crr[t - 1], xrr[t]);
			}
		}
		else if (temp == 'Q')
		{
			cin >> tp;
			cout << crr[tp] << endl;
		}
	}
}