Language: C++

#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
using ll = long long;
using ld = long double;
#define int ll
#define double ld
#define VARNAME(v) #v
using P = pair<int,int>;
constexpr  int MOD = 1000000007;
//constexpr  int MOD = 998244353;
constexpr ll INF = 1e16;
#pragma region tmp
constexpr double EPS = 1e-10;
constexpr double PI = 3.141592653589793;
const string endn = "\n";
const string abc="abcdefghijklmnopqrstuvwxyz";
const string ABC="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
template<class T1, class T2>ostream &operator<<(ostream &out, const pair<T1, T2> &o){out << "(" << o.first << ", " << o.second << ")";return out;}
template<class T> ostream &operator<<(ostream &out, const vector<T> &o){for(auto itr=o.begin();itr != o.end();itr++)out << *itr << (itr+1 != o.end() ? " " : "");return out;}
template<class T> ostream &operator<<(ostream &out, const deque<T> &o){for(auto itr=o.begin();itr != o.end();itr++)out << *itr << (itr+1 != o.end() ? " " : "");return out;}
template<class T> ostream &operator<<(ostream &out, const set<T> &o){out << "{";for(auto itr=o.begin();itr != o.end();itr++)out << *itr << (next(itr,1) != o.end() ? "," : "");out << "}";return out;}
template<class T> ostream &operator<<(ostream &out, const multiset<T> &o){out << "{";for(auto itr=o.begin();itr != o.end();itr++)out << *itr << (next(itr,1) != o.end() ? "," : "");out << "}";return out;}
template<class T, class U> ostream &operator<<(ostream &out, const map<T, U> &o){out << "{";for(auto itr=o.begin();itr != o.end();itr++)out << *itr << (next(itr,1) != o.end() ? " " : "");out << "}";return out;}
template<class T, class U> ostream &operator<<(ostream &out, const multimap<T, U> &o){out << "{";for(auto itr=o.begin();itr != o.end();itr++)out << *itr << (next(itr,1) != o.end() ? " " : "");out << "}";return out;}
template<class T> ostream &operator<<(ostream &out, queue<T> o){while(!o.empty())out << o.front() << (o.size() > 0 ? " " : ""),o.pop();return out;}
template<class T, class U> ostream &operator<<(ostream &out, priority_queue<T, vector<T>, U> o){while(!o.empty())out << o.top() << (o.size() > 0 ? " " : ""),o.pop();return out;}
template<class T> ostream &operator<<(ostream &out, stack<T> o){while(!o.empty())out << o.top() << (o.size() > 0 ? " " : ""),o.pop();return out;}
template<class T> inline bool chmin(T& a, T b){if(a>b){a = b;return 1;}return 0;}
template<class T> inline bool chmax(T& a, T b){if(a<b){a = b;return 1;}return 0;}
template<class T> inline bool chmin(T& a, initializer_list<T> b){T c = min(b);if(a>c){a = c;return 1;}return 0;}
template<class T> inline bool chmax(T& a, initializer_list<T> b){T c = max(b);if(a<c){a = c;return 1;}return 0;}
inline int mrep(int& a, int M=MOD){a%=M;return a=(a<0 ? a+M : a);}
inline int add(int& a, int b, int M=MOD){return a=(mrep(a,M)+mrep(b,M))%M;}
inline int mul(int& a, int b, int M=MOD){return a=(mrep(a,M)*mrep(b,M))%M;}
inline int add(int& a, initializer_list<int> b, int M=MOD){return a=(mrep(a,M)+accumulate(b.begin(), b.end(), (int)0, [&M](int acc, int i){return (acc+mrep(i,M))%M;}))%M;}
inline int mul(int& a, initializer_list<int> b, int M=MOD){return a=(mrep(a,M)*accumulate(b.begin(), b.end(), (int)1, [&M](int acc, int i){return (acc*mrep(i,M))%M;}))%M;}
inline int modpow(int b, int e, int M=MOD){int ret=1;while(e > 0){if(e%2)mul(ret,b,M);mul(b,b,M);e /= 2;};return ret;}
inline int modinv(int a, int M=MOD){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);}return mrep(u,M);}
template<class T> inline void print(T a){cout << a << endl;}
template<class T> inline void print(vector<T> a, int n){chmin(n,int(a.size()));rep(i,n)cout << a[i] << (i != n-1 ? " " : "\n");}
template<class T, size_t SIZE> inline void print(T (&a)[SIZE], int n=SIZE){chmin(n,int(SIZE));rep(i,n)cout << a[i] << (i != n-1 ? " ":"\n");}
#pragma #endregion tmp


int n,k,q,a[2100];P ind[2100];
int bit[2100];
void badd(int i, int x){
  while(i <= n){
    bit[i] += x;
    i += (i&-i);
  }
}
int sum(int i){
  int ret = 0;
  while(i > 0){
    ret += bit[i];
    i -= (i&-i);
  }
  return ret;
}
signed main(){
  int n,m;cin>>n>>m;
  vector<P> ans;
  int s = m, t = m+1;
  rep(i,m){
    ans.push_back(P(s--,t++));
    if((t-s)*2 == n)t++;
  }
  }
  rep(i,m)cout << ans[i].first << " " << ans[i].second << endl;
}


Compiler output:
a.cc:4:21: error: expected unqualified-id before 'for'
    4 | #define repd(i,a,b) for (int i=(a);i<(b);i++)
      |                     ^~~
a.cc:5:18: note: in expansion of macro 'repd'
    5 | #define rep(i,n) repd(i,0,n)
      |                  ^~~~
a.cc:73:3: note: in expansion of macro 'rep'
   73 |   rep(i,m)cout << ans[i].first << " " << ans[i].second << endl;
      |   ^~~
a.cc:73:7: error: 'i' does not name a type
   73 |   rep(i,m)cout << ans[i].first << " " << ans[i].second << endl;
      |       ^
a.cc:4:36: note: in definition of macro 'repd'
    4 | #define repd(i,a,b) for (int i=(a);i<(b);i++)
      |                                    ^
a.cc:73:3: note: in expansion of macro 'rep'
   73 |   rep(i,m)cout << ans[i].first << " " << ans[i].second << endl;
      |   ^~~
a.cc:73:7: error: 'i' does not name a type
   73 |   rep(i,m)cout << ans[i].first << " " << ans[i].second << endl;
      |       ^
a.cc:4:42: note: in definition of macro 'repd'
    4 | #define repd(i,a,b) for (int i=(a);i<(b);i++)
      |                                          ^
a.cc:73:3: note: in expansion of macro 'rep'
   73 |   rep(i,m)cout << ans[i].first << " " << ans[i].second << endl;
      |   ^~~
a.cc:74:1: error: expected declaration before '}' token
   74 | }
      | ^