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同 AcWing 950 鬱悶的出納員

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using p = pair<int, int>;
const int inf(0x3f3f3f3f);
const int maxn(1e5 + 10);
int idx, root;
char op[2];

struct node {
    int val, siz;
    int fa, ch[2];
} tree[maxn];

template<typename T = int>
inline const T read()
{
    T x = 0, f = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9') {
        if (ch == '-') f = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9') {
        x = (x << 3) + (x << 1) + ch - '0';
        ch = getchar();
    }
    return x * f;
}

template<typename T>
inline void write(T x, bool ln)
{
    if (x < 0) {
        putchar('-');
        x = -x;
    }
    if (x > 9) write(x / 10, false);
    putchar(x % 10 + '0');
    if (ln) putchar(10);
}

inline int new_node(int val)
{
    ++idx;
    tree[idx].val = val;
    tree[idx].siz = 1;
    return idx;
}

inline void push_up(int cur)
{
    tree[cur].siz = tree[tree[cur].ch[0]].siz + tree[tree[cur].ch[1]].siz + 1;
}

inline bool get_rel(int cur, int fa)
{
    return tree[fa].ch[1] == cur;
}

inline void connect(int cur, int fa, int rel)
{
    tree[fa].ch[rel] = cur;
    tree[cur].fa = fa;
}

inline void rotate(int cur)
{
    int fa = tree[cur].fa;
    int gf = tree[fa].fa;
    bool rel = get_rel(cur, fa);
    connect(tree[cur].ch[rel ^ 1], fa, rel);
    connect(cur, gf, get_rel(fa, gf));
    connect(fa, cur, rel ^ 1);
    push_up(fa);
    push_up(cur);
}

inline void splaying(int cur, int top)
{
    while (tree[cur].fa not_eq top) {
        int fa = tree[cur].fa;
        int gf = tree[fa].fa;
        if (gf not_eq top) {
            get_rel(cur, fa) ^ get_rel(fa, gf) ? rotate(cur) : rotate(fa);
        }
        rotate(cur);
    }
    if (not top) {
        root = cur;
    }
}

inline void insert(int val)
{
    int cur = root, fa = 0;
    while (cur) {
        fa = cur;
        cur = tree[cur].ch[val > tree[cur].val];
    }
    cur = new_node(val);
    connect(cur, fa, val > tree[fa].val);
    splaying(cur, 0);
}

inline int lower_bound(int val)
{
    int cur = root, res = 0;
    while (cur) {
        if (tree[cur].val >= val) {
            res = cur;
            cur = tree[cur].ch[0];
        } else {
            cur = tree[cur].ch[1];
        }
    }
    return res;
}

inline int get_val(int rank)
{
    int cur = root;
    while (cur) {
        if (tree[tree[cur].ch[0]].siz >= rank) {
            cur = tree[cur].ch[0];
        } else if (tree[tree[cur].ch[0]].siz + 1 == rank) {
            break;
        } else {
            rank -= tree[tree[cur].ch[0]].siz + 1;
            cur = tree[cur].ch[1];
        }
    }
    return tree[cur].val;
}

int main()
{
#ifdef ONLINE_JUDGE
#else
    freopen("input.txt", "r", stdin);
#endif
    int n = read(), m = read();
    insert(-inf);
    insert(inf);
    int d = 0, cnt = 0;
    while (n--) {
        scanf("%s", op);
        int k = read();
        if (*op == 'I' and k >= m) {
            insert(k - d);
            ++cnt;
        } else if (*op == 'A') {
            d += k;
        } else if (*op == 'S') {
            d -= k;
            int l = 1, r = lower_bound(m - d);
            splaying(r, 0);
            splaying(l, r);
            tree[l].ch[1] = 0;
            push_up(l);
            push_up(r);
        } else if (*op == 'F') {
            write(tree[root].siz - 2 >= k ? (get_val(tree[root].siz - k) + d) : -1, true);
        }
    }
    write(cnt + 2 - tree[root].siz, true);
    return 0;
}