Submission #4670942

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define _MACRO(_1, _2, _3, NAME, ...) NAME
#define _repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define _rep(i,n) _repl(i,0,n)
#define rep(...) _MACRO(__VA_ARGS__, _repl, _rep)(__VA_ARGS__)
#define pb push_back
#define all(x) begin(x),end(x)
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#ifdef LOCAL
#define dbg(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
void _dbg(string){cerr<<endl;}
template<class H,class... T> void _dbg(string s,H h,T... t){int l=s.find(',');cerr<<s.substr(0,l)<<" = "<<h<<", ";_dbg(s.substr(l+1),t...);}
template<class T,class U> ostream& operator<<(ostream &o, const pair<T,U> &p){o<<"("<<p.first<<","<<p.second<<")";return o;}
template<class T> ostream& operator<<(ostream &o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}
#else
#define dbg(...) {}
#endif

int main(){
  int n;
  cin>>n;

  using P = pair<int,int>;
  vector<P> ans;

  int bad;

  if(n%2==1){
    bad = n;
  }
  else {
    bad = n+1;
  }

  rep(i,n) rep(j,i+1,n) if(i+j+2 != bad) ans.push_back({i+1, j+1});

  cout << ans.size() << endl;
  for(auto p : ans) cout << p.first << " " << p.second << "\n";

  return 0;
}

Submission Info

Judge Result