text: #include <cstdio>
  #include <cmath>
  #include <vector>
  
  int main(){
  
      long n, k; scanf("%ld %ld\n", &n, &k);
      std::vector<long> id(n + 1);
      for(long p = 1; p <= n; p++){scanf("%ld ", &id[p]);}
  
      long current(0);
      while(k > 0){k -= ++current;}
      k += current;
      printf("%ld\n", id[k]);
  
      return 0;
  }
  