#include <bits/stdc++.h>
using namespace std;
int dx[9] = {1, 0, -1, 0, 1, 1, -1, -1};
int dy[9] = {0, 1, 0, -1, 1, -1, 1, -1};
struct edge {
  int st, ed;
  char col;
  edge() {
    this->st = 0;
    this->ed = 0;
    this->col = 0;
  }
  edge(int st, int ed, char col) {
    this->st = st;
    this->ed = ed;
    this->col = col;
  }
};
long long n, m;
long long a[2000001], b[2000001];
int main() {
  std::ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;
  for (int test_case = 0; test_case < t; ++test_case) {
    cin >> n >> m;
    string input;
    cin >> input;
    string s2 = "";
    for (int i = 0; i < n; ++i) {
      a[i] = 1000000000;
    }
    for (int i = 0; i < n; ++i) {
      if (a[i % m] == 1000000000) a[i % m] = (long long)input[i] - '0';
      s2 += input[i % m];
    }
    bool flg = 0;
    if (s2 < input) flg = 1;
    if (flg) {
      int i;
      for (i = 0; i < n; ++i) {
        if (a[i] == 1000000000) break;
      }
      i--;
      while (a[i] == 9) {
        a[i] = 0;
        i--;
      }
      a[i]++;
    }
    cout << n << '\n';
    for (int i = 0; i < n; ++i) {
      cout << a[i % m];
    }
    cout << '\n';
  }
}
