text: #include<bits/stdc++.h>
  using namespace std;
  
  vector <vector <string> > a_;
  
  vector <string> b_;
  
  int main(){
  
  	string s;
  	s.resize(10);
  	s[0]='b';
  	s[1]='a';
  	b_.push_back(s);
  	a_.push_back(b_	);
  	//s[1]='\0';
  	cout<<a_[0][0][0]<<endl;
  
  
  	return 0;
  }