Language: C++

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define pli pair<ll, int>
#define pil pair<int, ll>
#define pll pair<ll, ll>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, n) for (int i = l; i < (n); ++i)
#define sz(v) (int)v.size()
#define endl '\n'
const int inf = 1000000007;
const ll INF = 1e18;
// int mod = 998244353;
int mod = 1000000007;
#define abs(x) (x >= 0 ? x : -(x))
#define lb(v, x) (int)(lower_bound(all(v), x) - v.begin())
#define ub(v, x) (int)(upper_bound(all(v), x) - v.begin())
template<typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { if (a > b) { a = b; return 1; } return 0; }
template<typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { if (a < b) { a = b; return 1; } return 0; }
ll gcd(ll a, ll b) { if (b == 0) return a; return gcd(b, a % b); }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template<typename T, typename U> T pow_(T a, U b) { return b ? pow_(a * a, b / 2) * (b % 2 ? a : 1) : 1; }
ll modpow(ll a, ll b, ll _mod) { return b ? modpow(a * a % _mod, b / 2, _mod) * (b % 2 ? a : 1) % _mod : 1; }
template<class T, class U> ostream& operator << (ostream& os, const pair<T, U>& p) { os << p.F << " " << p.S; return os; }
template<class T> ostream& operator << (ostream& os, const vector<T>& vec) { rep(i, sz(vec)) { if (i) os << " "; os << vec[i]; } return os; }
template<class T> ostream& operator << (ostream& os, const set<T>& s) { for (auto e : s) os << e; return os; }
template<typename T> inline istream& operator >> (istream& is, vector<T>& v) { rep(j, sz(v)) is >> v[j]; return is; }
template<class T, class T2> inline void add(T &a, T2 b) { (a += b % mod) %= mod; if (a < 0) a += mod; }
template<class T> void operator += (vector<T>& v, vector<T> v2) { rep(i, sz(v2)) v.eb(v2[i]); }


void solve();

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(12); // debuged
  int T;
  T = 1;
  while (T--) solve();
}

void solve() {
  int n, k;
  cin >> n >> k;
  vector<ll> a(n);
  cin >> a;
  vector<ll> b, c;
  rep(i, n) {
    if (a[i] > 0) b.eb(a[i]);
    else if (a[i] < 0) c.eb(-a[i]);
  }
  sort(all(b), greater<>());
  rep3(i, 1, sz(b)) (b[i] *= b[i - 1]) %= mod; // [i - 1], not [i] - 1
  sort(all(c), greater<>());
  rep(i, sz(c)) {
    c[i] = -c[i] % mod + mod;
    c[i] %= mod;
  }
  rep3(i, 1, sz(c)) (c[i] *= c[i - 1]) %= mod;
  // cerr << b << endl << c << endl;

  ll ans = 0;
  rep(i, n) {
    int cnt = 2 * i + (k % 2);
    ll x = 1;

    if (cnt < 0 || cnt > sz(b)) continue;
    if (cnt) (x *= b[cnt - 1]) %= mod;
    int cnt2 = k - cnt;
    if (cnt2 < 0 || cnt2 > sz(c)) continue;
    if (cnt2) (x *= c[cnt2 - 1]) %= mod;
    chmax(ans, x);
  }
  // 負にしかできない場合
  if (sz(b) + sz(c) == n) { // 0 がない
    int flg = 0;
    if (k % 2 == 0) {
      if (sz(b) + sz(c) == k) {
        if (sz(c) % 2) flg = 1:
      } else {

      }
    } else {
      if (sz(b) + sz(c) == k) {
        if (sz(c) % 2) flg = 1;
      } else {
        if (sz(b) == 0) flg = 1;
      }
    }
    // cerr << "flg " << flg << endl;
    if (flg) {
      // とにかく絶対値小さいのを
      vector<pii> v(n);
      rep(i, n) v[i] = pii(abs(a[i]), a[i] > 0); // 0 はない
      sort(all(v));
      // rep(i, n) cerr << v[i] << endl;
      ans = 1;
      rep(i, k) {
        ll y = v[i].F;
        if (v[i].S == 0) (y = -y % mod + mod) %= mod;
        (ans *= y) %= mod;
      }
    }
  }
  cout << ans << endl;
}


Compiler output:
a.cc: In function 'void solve()':
a.cc:86:31: error: expected ';' before ':' token
   86 |         if (sz(c) % 2) flg = 1:
      |                               ^
      |                               ;