Language: C++

#include<bits/stdc++.h>
using namespace std;
 
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int main() {
    ll MOD = 10000007;
    int n,k;cin>>n>>k;
    pair<ll,int>a[n];
    
    int cc = 0;
    rep(i,n){
        ll tmp;cin>>tmp;
        a[i].first = abs(tmp);
        if(tmp>=0)a[i].second = 1;
        else {
            a[i].second = -1;
            ++cc;
        }
    }
    sort(a,a+n,greater<pair<ll,int>>());

    ll ans=1;
    ll tmp2,tmp3;
    
    int c1=0
    rep(i,k){
        if(a[i].second == -1)++c1;
    }
    if(cc==n && k%2==1){
        rep(i,k)ans=ans*a[n-i]%MOD;
    }
    else{
    rep(i,k)ans=ans*a[i]%MOD;
    if(c1%2==1){
        for(int i=k;i>=0;--i)if(a[i].second==1){
            tmp2=a[i].first;
            break;
        }
        for(int j=k+1;j<n;++j)if(a[j].second==-1){
            tmp3=a[j].first;
            break;
        }
        ans=(ans/tmp2*tmp3)%MOD;
    }
    }
    cout<<ans<<endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:5:19: error: expected ',' or ';' before 'for'
    5 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                   ^~~
a.cc:28:5: note: in expansion of macro 'rep'
   28 |     rep(i,k){
      |     ^~~
a.cc:28:9: error: 'i' was not declared in this scope
   28 |     rep(i,k){
      |         ^
a.cc:5:35: note: in definition of macro 'rep'
    5 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                   ^
a.cc:32:24: error: no match for 'operator*' (operand types are 'll' {aka 'long long int'} and 'std::pair<long long int, int>')
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                     ~~~^~~~~~~
      |                     |        |
      |                     |        std::pair<long long int, int>
      |                     ll {aka long long int}
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127,
                 from a.cc:1:
/usr/include/c++/14/complex:400:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const complex<_Tp>&)'
  400 |     operator*(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:400:5: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   mismatched types 'const std::complex<_Tp>' and 'll' {aka 'long long int'}
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
/usr/include/c++/14/complex:409:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const _Tp&)'
  409 |     operator*(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:409:5: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   mismatched types 'const std::complex<_Tp>' and 'll' {aka 'long long int'}
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
/usr/include/c++/14/complex:418:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const _Tp&, const complex<_Tp>&)'
  418 |     operator*(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:418:5: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   'std::pair<long long int, int>' is not derived from 'const std::complex<_Tp>'
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'll' {aka 'long long int'}
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'll' {aka 'long long int'}
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   'std::pair<long long int, int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'll' {aka 'long long int'}
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   'std::pair<long long int, int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const valarray<_Tp>&, const valarray<_Tp>&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   mismatched types 'const std::valarray<_Tp>' and 'll' {aka 'long long int'}
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   mismatched types 'const std::valarray<_Tp>' and 'll' {aka 'long long int'}
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:32:30: note:   'std::pair<long long int, int>' is not derived from 'const std::valarray<_Tp>'
   32 |         rep(i,k)ans=ans*a[n-i]%MOD;
      |                              ^
a.cc:35:20: error: no match for 'operator*' (operand types are 'll' {aka 'long long int'} and 'std::pair<long long int, int>')
   35 |     rep(i,k)ans=ans*a[i]%MOD;
      |                 ~~~^~~~~
      |                 |      |
      |                 |      std::pair<long long int, int>
      |                 ll {aka long long int}
/usr/include/c++/14/complex:400:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const complex<_Tp>&)'
  400 |     operator*(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:400:5: note:   template argument deduction/substitution failed:
a.cc:35:24: note:   mismatched types 'const std::complex<_Tp>' and 'll' {aka 'long long int'}
   35 |     rep(i,k)ans=ans*a[i]%MOD;
      |                        ^
/usr/include/c++/14/complex:409:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const _Tp&)'
  409 |     operator*(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:409:5: note:   template argument deduction/substitution failed:
a.cc:35:24: note:   mismatched types 'const std::complex<_Tp>' and 'll' {aka 'long long int'}
   35 |     rep(i,k)ans=ans*a[i]%MOD;
      |                        ^
/usr/include/c++/14/complex:418:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const _Tp&, const complex<_Tp>&)'
  418 |     operator*(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~