#include <iostream>
#include <cstring>
#include <algorithm>
#include <climits>
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;
    scanf("%d", &n);
    f[0] = INT_MIN;
    while (n -- ){
        char str[2];
        int x;
        scanf("%s",str);
        if(*str == 'I'){
            scanf("%d",&x);
            push_left(x);
        }
        else if(*str == 'D'){
            if(tl > 0) tl--;
        }
        else if(*str == 'L'){
            if(tl > 0)stkr[ ++ tr] = stkl[tl -- ];
        }
        else if(*str == 'R'){
            if(tr > 0)push_left(stkr[tr -- ]);
        }
        else{
            scanf("%d",&x);
            printf("%d\n",f[x]);
        }
    }
    return 0;
}