text: #include <iostream>
  
  unsigned int m, inc, i2;
  
  int main(){
  	std::cin>>m>>std::ws;
  	inc = 1;
  	i2 = 0;
  	for(unsigned int i = 0; i < m; ){
  		i += inc;
  		inc++;
  		i2++;
  	}
  	std::string s, s2 = "";
  	getline(std::cin, s);
  	inc = 1;
  	i2 = 0;
  	for(unsigned int i = 0; i < m; ){
  		s2 = s2 + s[i];
  		i += inc;
  		inc++;
  		i2++;
  	}
  	std::cout<<s2<<std::endl;
  	return 0;
  }