#include <cstdio>

#include <cstring>

#include <cstdlib>

#include <algorithm>

using namespace std;

const int MAXN = ;

const int INF =  << ;

struct node

{

    int val;

    node *next;

    node *pre;

};

int sum[MAXN];

int maxSum[MAXN];

int main()

{

    //freopen( "1004.in", "r", stdin );

    //freopen( "test.txt", "w", stdout );

    int Q;

    node *head = ( node *)malloc(sizeof(node));

    while ( scanf( "%d", &Q ) ==  )

    {

        head->pre = NULL;

        head->next = NULL;

        node *cur = head;

        maxSum[] = -INF;

        sum[] = ;

        int pos = ;

        char op[];

        int a;

        for ( int i = ; i < Q; ++i )

        {

            scanf( "%s", op );

            if ( op[] == 'I' )

            {

                scanf( "%d", &a );

                ++pos;

                sum[pos] = sum[pos-] + a;

                maxSum[pos] = max( sum[pos], maxSum[pos-] );

                node *p = (node *)malloc( sizeof(node) );

                p->val = a;

                p->next = NULL;

                p->pre = cur;

                if ( cur->next )

                {

                    p->next = cur->next;

                    cur->next->pre = p;

                }

                cur->next = p;

                cur = cur->next;

            }

            else if ( op[] == 'Q' )

            {

                scanf( "%d", &a );

                if ( pos < a ) a = pos;

                printf( "%d\n", maxSum[a] );

            }

            else if ( op[] == 'L' )

            {

                if ( cur->pre != NULL )

                {

                    cur = cur->pre;

                    --pos;

                }

            }

            else if ( op[] == 'R' )

            {

                //printf( "cur->next=%d %d\n", cur->next, NULL );

                if ( cur->next != NULL )

                {

                    cur = cur->next;

                    ++pos;

                    sum[pos] = sum[pos - ] + cur->val;

                    maxSum[pos] = max( sum[pos], maxSum[pos-] );

                }

            }

            else if ( op[] == 'D' )

            {

                --pos;

                node *p = cur;

                cur = p->pre;

                cur->next = p->next;

                if ( p->next )

                    p->next->pre = cur;

                free(p);

            }

/*

            node *pp = head->next;

            while ( pp )

            {

                printf( "%d ", pp->val );

                pp = pp->next;

            }

            puts("");

*/

        }

    }

    return ;

}