Language: C++

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cstdint>
#include <cstdlib>
#include <cmath>
#include <complex>
#include <chrono>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>
#include <random>
#include <utility>
#include <limits>
#include <list>
#include <type_traits>

/* template start */
 
#define rep(i, a, b) for (long long i = (a); (i) < (b); (i)++)
#define all(i) i.begin(), i.end()

#ifdef LOCAL
#define debug(...) std::cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

void debug_out(){std::cerr<<std::endl;}

template<typename Head,typename... Tail>
void debug_out(Head h,Tail... t){
  std::cerr<<" "<<h;
  if(sizeof...(t)>0)std::cout<<" :";
  debug_out(t...);
}
 
template <typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, std::pair<T1, T2> pa) {
  return os << pa.first << " " << pa.second;
}
 
template <typename T>
std::ostream& operator<<(std::ostream& os, std::vector<T> vec) {
  for (std::size_t i = 0; i < vec.size(); i++)os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}
 
template<typename T1,typename T2>
inline bool chmax(T1& a,T2 b){return a<b && (a=b,true);}
 
template<typename T1,typename T2>
inline bool chmin(T1& a,T2 b){return a>b && (a=b,true);}

template<typename Num>
constexpr Num mypow(Num a, long long b) {
  if(b==0)return 1;
  if (a==0)return 0;
  Num x = 1;
  while (b > 0) {
    if(b & 1)x*=a;
    a*=a;
    b >>= 1;
  }
  return x;
}

/* template end */

using ll = long long;

#include "../../../lib/utility/modint.hpp"

constexpr ll MOD=1e9+7;

using mint=modint<MOD>;

int main() {
  std::cin.tie(nullptr);
  std::ios::sync_with_stdio(false);

  ll n,k;
  std::cin>>n>>k;
  std::vector<ll> a(n);
  std::vector<ll> plus,minus;

  rep(i,0,n){
    ll t;
    std::cin>>t;
    a[i]=t;
    if(t>=0)plus.emplace_back(t);
    if(t<0)minus.emplace_back(t);
  }

  if(k==n){
    mint ans=1;
    rep(i,0,n)ans*=(MOD+a[i]);
    std::cout<<ans.value()<<"\n";
    return 0;
  }

  if(plus.empty()){
    if(k%2){
      std::sort(all(minus),std::greater<ll>());
      mint ans=1;
      rep(i,0,k)ans*=(MOD+minus[i]);
      std::cout<<ans.value()<<"\n";
      return 0;
    }else{
      std::sort(all(minus));
      mint ans=1;
      rep(i,0,k)ans*=(MOD+minus[i]);
      std::cout<<ans.value()<<"\n";
      return 0;
    }
  }

  std::sort(all(minus));
  std::sort(all(plus),std::greater<ll>());

  debug(plus);
  debug(minus);

  mint ans=1;
  if(k%2){
    ans*=plus[0];
    plus.erase(plus.begin());
  }

  ll p=plus.size(),m=minus.size();

  std::vector<ll> plus_pair(p/2),minus_pair(m/2);

  rep(i,0,p/2)plus_pair[i]=plus[2*i]*plus[2*i+1];
  rep(i,0,m/2)minus_pair[i]=minus[2*i]*minus[2*i+1];

  ll pn=0,mn=0;


  rep(i,0,k/2){
    if(pn==p/2){
      ans*=minus_pair[mn];
      mn++;
    }else if(mn==m/2){
      ans*=plus_pair[pn];
      pn++;
    }else{
      if(plus_pair[pn]>minus_pair[mn]){
        ans*=plus_pair[pn];
        pn++;
      }else{
        ans*=minus_pair[mn];
        mn++;
      }
    }
  }

  std::cout<<ans.value()<<"\n";

  return 0;
}

Compiler output:
a.cc:84:10: fatal error: ../../../lib/utility/modint.hpp: No such file or directory
   84 | #include "../../../lib/utility/modint.hpp"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.