acm.sgu.ru/lang problem-2049

#include <stdio.h>
#include <stack>
#include <math.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <string>
#include <set>
#include <memory.h>
#include <vector>
#include <map>
#include <queue>
#include <iomanip>
#include <ctime>
#include <cassert>



#define forn(i, n) for (int i = 0; i < int(n); i++)
#define ll long long
#define mp(a, b) make_pair(a, b)
#define sqr(x) ( (x) * (x) )
#define all(a) a.begin(), a.end()

using namespace std;

typedef pair <int, int> pt;
typedef long double ld;
const int INF = 1e9;
const ld EPS = 1e-9;

int a[101];

int main() {
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int t, m;
    cin >> t >> m;
    int id = 1;
    forn (i, t) {
        string s;
        int x;
        cin >> s;
        if (s == "alloc") {
            cin >> x;
            bool ok = true;
            if (x > m) {
                cout << "NULL" << endl;
                continue;
            }
            forn (j, m - x + 1) {
                ok = true;
                for (int k = j; k < j + x && ok; k++) {
                    if (a[k] != 0)
                        ok = false;
                }
                if (ok) {
                    for (int k = j; k < j + x && ok; k++) {
                        a[k] = id;
                    }
                    cout << id << endl;
                    id++;
                    break;
                }
            }
            if (!ok)
                cout << "NULL" << endl;
        }
        if (s == "erase") {
            cin >> x;
            if (x < 1) {
                cout << "ILLEGAL_ERASE_ARGUMENT" << endl;
                continue;
            }
            bool ok = false;
            forn (j, m) {
                if (a[j] == x) {
                    a[j] = 0;
                    ok = true;
                }
            }
            if (!ok) {
                cout << "ILLEGAL_ERASE_ARGUMENT" << endl;
            }
        }
        if (s == "defragment") {
            forn (j, m) {
                int k = j;
                while (k != 0 && a[k] != 0 && a[k - 1] == 0) {
                    a[k - 1] = a[k];
                    a[k] = 0;
                    k--;
                }
            }
        }
    }
    return 0;
}