3 3
1 2
3 1
2 3
 2 0
 10 17
1 2
1 3
1 4
1 5
1 6
1 7
1 8
1 9
1 10
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 10
 2 1
1 2
 8 13
1 2
2 3
3 4
4 1
2 4
1 3
5 6
6 7
7 8
8 5
6 8
5 7
1 8
 3 2
1 2
2 3
 10 9
1 2
1 3
1 4
1 5
1 6
1 7
1 8
1 9
1 10
 10 40
1 3
2 6
9 10
4 6
1 2
1 8
6 10
3 6
1 4
5 7
3 8
3 9
4 5
3 7
8 9
5 9
5 6
2 3
3 4
1 6
4 8
3 10
5 10
2 8
2 10
4 7
1 10
1 7
4 10
5 8
8 10
7 9
6 8
2 7
4 9
6 9
7 8
6 7
1 5
2 9
 10 9
1 2
2 3
3 1
4 5
5 6
6 7
7 4
4 6
5 7
 1000000 0
 8 11
1 2
1 3
1 4
2 3
2 7
7 4
4 2
7 5
8 1
1 7
7 8
 9 9
1 2
2 3
3 1
4 5
5 6
6 4
7 8
8 9
9 7
 15 14
1 2
1 3
1 4
1 5
2 6
2 7
7 8
7 9
3 10
10 11
4 12
12 13
13 14
13 15
 10 17
1 2
1 3
1 4
1 5
1 6
1 7
1 8
1 9
1 10
2 3
2 4
2 5
2 6
2 7
2 8
2 9
2 10
 9 12
1 2
2 3
3 1
1 4
4 5
5 1
1 6
6 7
7 1
1 8
8 9
9 1
 3 1
1 2
 10 5
5 7
4 8
9 10
7 10
6 10
 15 15
1 2
1 3
1 4
1 5
2 6
2 7
7 8
7 9
3 10
10 11
4 12
12 13
13 14
13 15
15 1
 4 3
1 2
2 3
3 1
 10 30
4 9
4 6
1 2
8 10
7 8
4 7
1 8
6 7
5 6
1 5
7 9
1 7
8 9
7 10
9 10
3 9
2 7
5 7
5 9
2 8
2 9
5 8
3 10
1 6
3 6
2 10
6 8
3 4
2 5
4 5
 4 3
1 2
1 3
1 4
 4 6
1 2
2 3
3 4
4 1
1 3
2 4
 10 9
1 2
1 3
1 4
2 5
5 6
2 7
3 8
3 9
9 10
 10 10
1 2
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 10
10 1
 3 0
 6 6
1 2
2 3
3 1
4 5
5 6
6 4
 10 0
 9 15
1 2
2 3
3 1
1 4
4 5
5 1
1 6
6 7
7 1
1 8
8 9
9 1
2 9
7 4
2 8
 4 0
 1 0

1
 0
 43
 0
 8
 0
 84
 82
 63
 166666166667000000
 21
 30
 292
 64
 36
 0
 84
 284
 1
 37
 1
 4
 59
 50
 1
 2
 120
 28
 4
 0

#include <bits/stdc++.h>
int t, m, num = 1;
int mem[1005];
int r[1005];
char o[1005][15];
int on[1005];
int cmp(const void *p1, const void *p2) { return *(int *)p1 - *(int *)p2; }
void all(int l) {
  int i, j, flag = 0;
  r[num] = on[l];
  for (i = 0; i < m; i++) {
    if (mem[i] == 0) {
      flag = 0;
      for (j = i; j < i + on[l] && j < m; j++) {
        if (mem[j] != 0) break;
      }
      if (j - i < on[l]) flag = 1;
      if (flag == 1) continue;
      if (flag == 0) {
        for (j = i; j < i + on[l]; j++) mem[j] = num;
        printf("%d\n", num);
        flag = 2;
      }
    }
    if (flag == 2) break;
  }
  if (flag != 2) {
    printf("NULL\n");
    num--;
  }
}
void era(int l) {
  int i;
  if (r[on[l]] == 0)
    printf("ILLEGAL_ERASE_ARGUMENT\n");
  else {
    for (i = 0; i < m; i++) {
      if (mem[i] == on[l]) mem[i] = 0;
    }
    r[on[l]] = 0;
  }
}
void def() {
  int i, j, k;
  for (i = 0; i < m; i++) {
    if (mem[i] == 0) {
      for (j = i + 1; j < m; j++) {
        if (mem[j] != 0) {
          k = mem[j];
          mem[j] = mem[i];
          mem[i] = k;
        }
      }
    }
  }
}
int main() {
  int i;
  scanf("%d%d", &t, &m);
  memset(mem, 0, sizeof(mem));
  for (i = 0; i < t; i++) {
    scanf("%s", o[i]);
    if (o[i][0] == 'd') {
      def();
    } else {
      scanf("%d", &on[i]);
      if (o[i][0] == 'a') {
        all(i);
        num++;
      }
      if (o[i][0] == 'e') era(i);
    }
  }
  return 0;
}
