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#include <string>
#include <vector>
#include <iostream>
#include <unordered_map>

typedef long long ll;

int main() {
  ll n, k;
  ll maxK = 1000000000LL
           *1000000000LL;
  std::cin >> n >> k;
  
  std::vector< ll > powsum(n);
  powsum[n-1] = 1;
  for(int i = n-2; i >= 0; i--) {
    powsum[i] = std::min(powsum[i+1] * 2 + 1, maxK);
  }
  
  std::string res = "";
  k--;
  int letterInd = k / powsum[0];
  if(letterInd == 0) {
    res += "a";
  } else if(letterInd == 1) {
    res += "b";
  } else if(letterInd == 2) {
    res += "c";
  } else {
    printf("NIE\n");
    return 0;
  }
  k -= letterInd * powsum[0];

  std::unordered_map< char, char > firstNext  {{'a', 'b'}, {'b', 'a'}, {'c', 'a'}};
  std::unordered_map< char, char > secondNext {{'a', 'c'}, {'b', 'c'}, {'c', 'b'}};

  for(int i = 1; i < n && k != 0; i++) {
    k--;
    letterInd = k / powsum[i];
    if(letterInd == 0) {
      res += firstNext[res.back()];
    } else {
      res += secondNext[res.back()];
    }
    k -= letterInd * powsum[i];
  }
  
  std::cout << res << std::endl;
  
  return 0;
}