#include <iostream>
#include <algorithm>
#include <limits.h>
using namespace std;
const int N = 1E6 + 10;
int stkl[N], stkr[N], tl, tr;
int s[N], f[N];
void push_left(int x){
    stkl[ ++ tl] = x;
    s[tl] = s[tl - 1] + x;
    f[tl] = max(f[tl - 1], s[tl]);
}
int main(){
    int n;  cin >> n;
    f[0] = INT_MIN;
    while(n -- ){
        char op[5];
        cin >> op;
        int x;
        if(op[0] == 'I'){
            cin >> x;
            push_left(x);
        }else if(op[0] == 'D'){
            if(tl > 0)  tl -- ;
        }else if(op[0] == 'L'){
            if(tl > 0){
                x = stkl[tl -- ];
                stkr[ ++ tr] = x;
            }
        }else if(op[0] == 'R'){
            if(tr > 0){
                x = stkr[tr -- ];
                push_left(x);
            }
        }else{
            cin >> x;
            cout << f[x] << endl;
        }
    }
    return 0;
}