C.cpp

#include<iostream>
#include<deque>
#include<queue>
using namespace std;
 
deque<char> deq;
 
void check(){
  //cout << "check" << endl;
  deque<char> que;
  int j = deq.size();
  for(int i = 0; i < j; i++){
    //cout << deq.front() << ' ' << que.back() << endl;
    if(que.size() == 0 || deq.front() != que.back()){
      que.push_back(deq.front());
      deq.pop_front();
    }
    else{
      deq.pop_front();
      que.pop_back();
    }
  }
  j = que.size();
  for(int i = 0; i < j; i++){
    deq.push_back(que.front());
    que.pop_front();
  }
    
}
 
int main(void){
  int n;
  cin >> n;
  char str[55];
  cin >> str;
  for(int i = 0; i < n; i++){
    if(deq.size() < 2){
      deq.push_back(str[i]);
    }else{
      bool b = false;
      if(str[i] == deq.front()) b = true;
      else if(str[i] == deq.back()) b = false;
      else {
       for(int j = 0; j < deq.size() / 2; j++){
          if(deq.at(j) == deq.at(deq.size()-1 - j)) continue;
          for(int k = i; k < n; k++){
            if(str[k] == deq.at(j)){
	      break;
	    }
            if(str[k] == deq.at(deq.size()-1 - j)){
	      b = true;
	      break;
	    }
          }
        }
      }
      if(b){
      	deq.push_front(str[i]);
      }else{
      	deq.push_back(str[i]);
      }
    }
    //for(int j = 0; j < deq.size(); j++){
    //  cout << deq.at(j);
    //}
    //cout << endl;
    check();
  }
  cout << deq.size() << endl;
  return 0;
}