Language: C++

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define fo(a,b) for(int a=0;a<b;a++)
#define Sort(a) sort(a.begin(),a.end())
#define rev(a) reverse(a.begin(),a.end())
#define fi first
#define se second
#define sz size()
#define bgn begin()
#define en end()
#define pb push_back
#define pp() pop_back()
#define V vector
#define P pair
#define yuko(a) setprecision(a)
#define uni(a) a.erase(unique(a.begin(),a.end()),a.end())
#define Q queue
#define pri priority_queue
#define Pri priority_queue<int,vector<int>,greater<int>>
#define PriP priority_queue<P<int,int>,vector<P<int,int>>,greater<P<int,int>>>
#define ff first.first
#define fs first.second
#define sf second.first
#define ss second.second
#define all(a)  (a).begin(),(a).end()
#define elif else if
int low(V<int> a,int b){
  decltype(a)::iterator c=lower_bound(a.begin(),a.end(),b);
  int d=c-a.bgn;
  return d;
}
int upp(V<int> a,int b){
  decltype(a)::iterator c=upper_bound(a.begin(),a.end(),b);
  int d=c-a.bgn;
  return d;
}
template<class T>
 void cou(vector<vector<T>> a){
  int b=a.size();
  int c=a[0].size();
  fo(i,b){
    fo(j,c){
      cout<<a[i][j];
      if(j==c-1)
        cout<<endl;
      else
        cout<<' ';
    }
  }
}
int wari(int a,int b) {
  if(a%b==0)
    return a/b;
  else
    return a/b+1;
}
int keta(int a){
  double b=a;
  b=log10(b);
  int c=b;
  return c+1;
}
int souwa(int a){
  return a*(a+1)/2;
}
int gcm(int a,int b){
  if(a%b==0)
    return b;
  return gcm(b,a%b);
}
bool prime(int a){
  if(a<2)
    return false;
  else if(a==2)
    return true;
  else if(a%2==0)
    return false;
  for(int i=3;i<=sqrt(a)+1;i+=2){
    if (a%i==0)
      return false;
  }
  return true;
}
struct Union{
  vector<int> par;
  Union(int a){
  par=vector<int>(a,-1);
  }
  int find(int a){
    if(par[a]<0)
      return a;
    else
      return par[a]=find(par[a]);
  }
  bool same(int a,int b){
    return find(a)==find(b);
  }
  int Size(int a){
    return -par[find(a)];
  }
  void unite(int a,int b){
    a=find(a);
    b=find(b);
    if(a==b)
      return;
    if(Size(b)>Size(a))
      swap<int>(a,b);
    par[a]+=par[b];
    par[b]=a;
  }
};
int ketas(int a){
  string b=to_string(a);
  int c=0;
  fo(i,keta(a)){
    c+=b[i]-'0';
  }
  return c;
}
bool fe(int a,int b){
  a%=10;
  b%=10;
  if(a==0)
    a=10;
  if(b==0)
    b=10;
  if(a>b)
    return true;
  else
    return false;
}
int INF=1000000007;
struct edge{int s,t,d; };
V<int> mojisyu(string a){
  V<int> b(26,0);
  fo(i,a.sz){
    b[a[i]-'a']++;
  }
  return b;
}
int wa2(int a){
  if(a%2==1)
    return a/2;
  return a/2-1;
}
/*signed main(){
  int a,b,c;
  cin>>a>>b>>c;
  V<V<edge>> d(a);
  fo(i,b){
    edge e;
    cin>>e.s>>e.t>>e.d;
    d[e.s].pb(e);
  }
  V<int> e(a,INF);
  e[c]=0;
  priority_queue<P<int,int>,V<P<int,int>>,greater<P<int,int>>> f;
  f.push({0,c});
  int h=INF;
  while(!f.empty()){
    P<int,int> g;
    g=f.top();
    f.pop();
    int v = g.second, i = g.first;
    for(edge l : d[v]){
      if(e[l.t] > i + l.d){
        e[l.t] = i + l.d;
        f.push({i+l.d , l.t});
      }
    }
  }
  fo(i,a){
    if(e[i]==INF)
      cout<<"INF"<<endl;
    else
      cout<<e[i]<<endl;
  }
}
?*/
int nCr(int n,int r){
  int a=1;
  r=min(r,n-r);
  for(int i=n;i>n-r;i--){
    a*=i;
    a/=n-i+1;
  }
  return a;
}
/*void sea(int x,int y){
  if(x<0||a<=x||y<0||b<=y||c[x][y]=='#')
    return;
  if(d[x][y])
    return;
  d[x][y]++;
  sea(x+1,y);
  sea(x-1,y);
  sea(x,y+1);
  sea(x,y-1);
}*/
int kaijou(int a){
  int b=1;
  fo(i,a)
    b*=i+1;
  return b;
}
int nPr(int a,int b){
  if(a<b)
    return 0;
  if(b==0)
    return 1;
  int c=1;
  for(int i=a;i>a-b;i--){
    c*=i;
    c%=INF;
  }
  return c;
}
int modinv(int a,int m){
  int b=m,u=1,v=0;
  while(b){
    int t=a/b;
    a-=t*b;
    swap(a,b);
    u-=t*v;
    swap(u,v);
  }
  u%=m;
  if(u<0)
    u+=m;
  return u;
}
int lcm(int a,int b){
  int c=modinv(gcm(a,b),INF);
  return ((a*c)%INF)*(b%INF)%INF;
}
int MOD=INF;
int fac[1000010], finv[1000010], inv[1000010]; 
// テーブルを作る前処理
//先にCOMinit()で前処理をする
//ABC145D
void COMinit() {
  fac[0]=fac[1]=1;
  finv[0]=finv[1]=1;
  inv[1]=1;
  for(int i=2;i<1000010;i++){
    fac[i]=fac[i-1]*i%MOD;
    inv[i]=MOD-inv[MOD%i]*(MOD/i)%MOD;
    finv[i]=finv[i-1]*inv[i]%MOD;
  }
}
// 二項係数計算
int COM(int n,int k){
  if(n<k)
    return 0;
  if(n<0||k<0)
    return 0;
  return fac[n]*(finv[k]*finv[n-k]%MOD)%MOD;
}
bool naka(int a,int b,V<V<char>> c){
  return (a>=0&&b>=0&&a<c.sz&&b<c[0].sz);
}

V<P<int,int>> mawari8={{0,-1},{0,1},{1,0},{-1,0},{-1,-1},{1,1},{1,-1},{-1,-1}};
int inf=1000000000000000007;
/*
signed main(){
  int a,b,c;
  cin>>a>>b>>c;
  V<V<edge>> d(a);
  fo(i,b){
    edge e;
    cin>>e.s>>e.t>>e.d;
    d[e.s].pb(e);
  }
  V<int> e(a,INF);
  e[c]=0;
  priority_queue<P<int,int>,V<P<int,int>>,greater<P<int,int>>> f;
  f.push({0,c});
  int h=INF;
  while(!f.empty()){
    P<int,int> g;
    g=f.top();
    f.pop();
    int v = g.second, i = g.first;
    for(edge l : d[v]){
      if(e[l.t] > i + l.d){
        e[l.t] = i + l.d;
        f.push({i+l.d , l.t});
      }
    }
  }
  fo(i,a){
    if(e[i]==INF)
      cout<<"INF"<<endl;
    else
      cout<<e[i]<<endl;
  }
}*/
V<P<int,int>> mawari4={{0,-1},{0,1},{1,0},{-1,0}};
//最短経路の表 a(全部INFで初期化)
//縦横 x,y
//迷路 f
//スタートsx,sy
//ゴールgx,gy
//文字はgから使おうね
/*int bfs_haba(){
  Q<P<int,int>> b;
  a[sx][sy]=0;
  b.push({sx,sy});
  while(!b.empty()){
    P<int,int> c=b.front();
    b.pop();
    if(c.fi==gx&&c.se==gy){
      break;
    }
    fo(i,4){
      int d=c.fi+mawari4[i].fi;
      int e=c.se+mawari4[i].se;
      if(0<=d&&0<=e&&d<x&&e<y&&f[d][e]!='#'&&a[d][e]==INF){
        b.push({d,e});
        a[d][e]=1+a[c.fi][c.se];
      }
    }
  }
  return a[gx][gy];
}*/
V<int> onajibubun(string a){
  V<int> b(a.sz);
  for(int i=1,j=0;i<a.sz;i++){
    if(i+b[i-j]<j+b[j])
      b[i]=b[i-j];
    else{
      int c=max<int>(0,j+b[j]-i);
      while(i+c<a.sz&&a[c]==a[i+c])
        c++;
      b[i]=c;
      j=i;
    }
  }
  b[0]=a.sz;
  return b;
}
//各頂点ごとにどこに辺が出てるかの表がc
//各頂点ごとの色を表すV<int>(頂点数max)のcolorを用意する
//aはどこ塗るか、bは何で塗るかなので、(0,1,c)でよぶとおけ
V<int> color(205);
bool nibu_hantei(int a,int b,V<V<int>> c){
  color[a]=b;
  fo(i,c[a].sz){
    if(b==color[c[a][i]])
      return false;
    if(color[c[a][i]]==0&&!nibu_hantei(c[a][i],-b,c))
      return false;
  }
  return true;
}
//aは頂点数
//nibu_hanteiの上にcolorを用意する
//各頂点ごとにどこに辺が出てるかの表がc
bool renketujanai_nibu_hantei(int a,V<V<int>> c){
  fo(i,a){
    if(color[i]==0){
      if(!nibu_hantei(i,1,c))
        return false;
    }
  }
  return true;
}
signed main(){
  int a;
  cin>>a;
  V<P<int,P<int,int>>> b(a),c;
  fo(i,a){
    cin>>b[i].fi;
    b[i].sf=i%2;
  }
  c=b;
  Sort(c);
  int c=0,d=0;
  fo(i,b){
    if(i%2!=b[c[i].ss].sf){
      if(i)
        c++;
      else
        d++;
    }
  }
  cout<<max(c,d)<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:381:7: error: conflicting declaration 'long long int c'
  381 |   int c=0,d=0;
      |       ^
a.cc:374:29: note: previous declaration as 'std::vector<std::pair<long long int, std::pair<long long int, long long int> > > c'
  374 |   V<P<int,P<int,int>>> b(a),c;
      |                             ^
a.cc:5:30: error: no match for 'operator<' (operand types are 'long long int' and 'std::vector<std::pair<long long int, std::pair<long long int, long long int> > >')
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                              ^
a.cc:382:3: note: in expansion of macro 'fo'
  382 |   fo(i,b){
      |   ^~
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1143:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1143 |     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1143:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/bits/regex.h:1224:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1224 |     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/bits/regex.h:1317:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1317 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/bits/regex.h:1391:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1391 |     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   'std::vector<std::pair<long long int, std::pair<long long int, long long int> > >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/bits/regex.h:1485:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1485 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/bits/regex.h:1560:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1560 |     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   'std::vector<std::pair<long long int, std::pair<long long int, long long int> > >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/bits/regex.h:1660:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1660 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'const std::pair<_T1, _T2>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/string_view:673:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  673 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:673:5: note:   template argument deduction/substitution failed:
a.cc:382:8: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'long long int'
  382 |   fo(i,b){
      |        ^
a.cc:5:31: note: in definition of macro 'fo'
    5 | #define fo(a,b) for(int a=0;a<b;a++)
      |                               ^
/usr/include/c++/14/string_view:680:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  680 |     operator< (basic_string_view<_CharT