Language: C++

#include <bits/stdc++.h>
#define rep(i,n)for(long long i=0;i<(n);i++)
using namespace std;
typedef long long ll;
typedef long double ld
typedef pair<int,int> P;
 
const int MOD=1000000007;
const int INF=0x3f3f3f3f;
const ll INFL=0x3f3f3f3f3f3f3f3f;
ll gcd(ll x, ll y){
  if(y==0) return x;
  else return gcd(y, x%y);
}
ll lcm(ll x,ll y){
  ll g=gcd(x,y);
  return x/g*y;
}




int main(){  
  int n;
  cin>>n;
  vector<int>x(n);
  vector<int>y(n);
  rep(i,n) cin>>x[i]>>y[i];
  ld ave=0;
  rep(i,n){
    rep(j,n){
      if(i!=j)ave+=sqrt(pow(x[i]-x[j],2)+pow(y[i]-y[j],2))
    }
  }#include <bits/stdc++.h>
#define rep(i,n)for(long long i=0;i<(n);i++)
using namespace std;
typedef long long ll;
typedef long double ld
typedef pair<int,int> P;
 
const int MOD=1000000007;
const int INF=0x3f3f3f3f;
const ll INFL=0x3f3f3f3f3f3f3f3f;
ll gcd(ll x, ll y){
  if(y==0) return x;
  else return gcd(y, x%y);
}
ll lcm(ll x,ll y){
  ll g=gcd(x,y);
  return x/g*y;
}




int main(){  
  int n;
  cin>>n;
  vector<int>x(n);
  vector<int>y(n);
  rep(i,n) cin>>x[i]>>y[i];
  ld ave=0;
  rep(i,n){
    rep(j,n){
      if(i!=j)ave+=sqrt(pow(x[i]-x[j],2)+pow(y[i]-y[j],2))
    }
  }
  ave/=n;
  cout<<ave<<endl;
}

Compiler output:
a.cc:34:4: error: stray '#' in program
   34 |   }#include <bits/stdc++.h>
      |    ^
a.cc:6:1: error: expected initializer before 'typedef'
    6 | typedef pair<int,int> P;
      | ^~~~~~~
a.cc: In function 'int main()':
a.cc:29:3: error: 'ld' was not declared in this scope; did you mean 'll'?
   29 |   ld ave=0;
      |   ^~
      |   ll
a.cc:32:15: error: 'ave' was not declared in this scope
   32 |       if(i!=j)ave+=sqrt(pow(x[i]-x[j],2)+pow(y[i]-y[j],2))
      |               ^~~
a.cc:34:5: error: 'include' was not declared in this scope
   34 |   }#include <bits/stdc++.h>
      |     ^~~~~~~
a.cc:34:14: error: 'bits' was not declared in this scope
   34 |   }#include <bits/stdc++.h>
      |              ^~~~
a.cc:34:19: error: 'stdc' was not declared in this scope; did you mean 'std'?
   34 |   }#include <bits/stdc++.h>
      |                   ^~~~
      |                   std
a.cc:36:1: error: expected primary-expression before 'using'
   36 | using namespace std;
      | ^~~~~
a.cc:39:1: error: expected initializer before 'typedef'
   39 | typedef pair<int,int> P;
      | ^~~~~~~
a.cc:44:19: error: a function-definition is not allowed here before '{' token
   44 | ll gcd(ll x, ll y){
      |                   ^
a.cc:48:18: error: a function-definition is not allowed here before '{' token
   48 | ll lcm(ll x,ll y){
      |                  ^
a.cc:56:9: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   56 | int main(){
      |         ^~
a.cc:56:9: note: remove parentheses to default-initialize a variable
   56 | int main(){
      |         ^~
      |         --
a.cc:56:9: note: or replace parentheses with braces to value-initialize a variable
a.cc:56:11: error: a function-definition is not allowed here before '{' token
   56 | int main(){
      |           ^
a.cc:70:2: error: expected '}' at end of input
   70 | }
      |  ^
a.cc:23:11: note: to match this '{'
   23 | int main(){
      |           ^