#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <climits>
#include <map>
#include <queue>
#include <set>
#include <cstring>
#include <vector>

using namespace std;
typedef long long ll;

int main() {
  int N, K;
  cin >> N >> K;
  string S;
  cin >> S;

  int colors[N][3];
  memset(colors, -1, sizeof(colors));

  for (int i = 0; i < N; ++i) {
    colors[i][0] = S[i] - '0';
  }
  
  for (int i = 1; i <= 2; ++i) {
    for (int j = 0; j < N - i; ++j) {
      colors[j][i] = !(colors[j][i - 1] & colors[j + 1][i - 1]);
    }
  }

  int offset = 0;
  int k = N - K;
  while (k >= 3) {
    k -= 2;
    offset += 1;
  }

  string ans = "";
  // fprintf(stderr, "k: %d\n", k);

  for (int i = 0; i < K; ++i) {
    if (colors[i + offset][k] == 0) {
      ans += '0';
    } else {
      ans += '1';
    }
  }

  cout << ans << endl;

  return 0;
}