Problem p03170 (C++)

Buggy submission (status: Runtime Error):
#include "bits/stdc++.h"
#include <random>
using namespace std;
typedef long long int lint;
typedef pair<lint, lint> plint;
typedef pair<double long, double long> pld;
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define POW2(n) (1LL << (n))
#define FOR(i, begin, end)                                                     \
  for (lint i = (begin), i##_end_ = (end); i < i##_end_; i++)
#define IFOR(i, begin, end)                                                    \
  for (lint i = (end)-1, i##_begin_ = (begin); i >= i##_begin_; i--)
#define REP(i, n) FOR(i, 0, n)
#define IREP(i, n) IFOR(i, 0, n)
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T1, typename T2>
pair<T1, T2> operator+(const pair<T1, T2> &l, const pair<T1, T2> &r) {
  return make_pair(l.first + r.first, l.second + r.second);
}
template <typename T1, typename T2>
pair<T1, T2> operator-(const pair<T1, T2> &l, const pair<T1, T2> &r) {
  return make_pair(l.first - r.first, l.second - r.second);
}
const lint MOD = 1e9 + 7, INF = 1e18;

lint dp[100001];
lint N, K, arr[100];

lint mex(lint curr) {
  set<lint> st;
  REP(i, N) {
    if (curr - arr[i] < 0)
      continue;
    if (dp[curr - arr[i]] == INF)
      continue;
    st.insert(dp[curr - arr[i]]);
  }
  REP(i, N) {
    if (st.find(i) == st.end()) {
      return i;
    }
  }
}

int main() {
  cin >> N >> K;
  REP(i, N) { cin >> arr[i]; }
  REP(i, K + 1) dp[i] = INF;
  REP(i, K + 1) {
    if (i < arr[0])
      dp[i] = 0;
    else
      dp[i] = mex(i);
  }
  if (dp[K] == 0)
    cout << "Second" << endl;
  else
    cout << "First" << endl;
}


Fixed submission:
#include "bits/stdc++.h"
#include <random>
using namespace std;
typedef long long int lint;
typedef pair<lint, lint> plint;
typedef pair<double long, double long> pld;
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define POW2(n) (1LL << (n))
#define FOR(i, begin, end)                                                     \
  for (lint i = (begin), i##_end_ = (end); i < i##_end_; i++)
#define IFOR(i, begin, end)                                                    \
  for (lint i = (end)-1, i##_begin_ = (begin); i >= i##_begin_; i--)
#define REP(i, n) FOR(i, 0, n)
#define IREP(i, n) IFOR(i, 0, n)
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T1, typename T2>
pair<T1, T2> operator+(const pair<T1, T2> &l, const pair<T1, T2> &r) {
  return make_pair(l.first + r.first, l.second + r.second);
}
template <typename T1, typename T2>
pair<T1, T2> operator-(const pair<T1, T2> &l, const pair<T1, T2> &r) {
  return make_pair(l.first - r.first, l.second - r.second);
}
const lint MOD = 1e9 + 7, INF = 1e18;

lint dp[100001];
lint N, K, arr[100];

lint mex(lint curr) {
  set<lint> st;
  REP(i, N) {
    if (curr - arr[i] < 0)
      continue;
    if (dp[curr - arr[i]] == INF)
      continue;
    st.insert(dp[curr - arr[i]]);
  }
  REP(i, N + 1) {
    if (st.find(i) == st.end()) {
      return i;
    }
  }
}

int main() {
  cin >> N >> K;
  REP(i, N) { cin >> arr[i]; }
  REP(i, K + 1) dp[i] = INF;
  REP(i, K + 1) {
    if (i < arr[0])
      dp[i] = 0;
    else
      dp[i] = mex(i);
  }
  if (dp[K] == 0)
    cout << "Second" << endl;
  else
    cout << "First" << endl;
}