#include <bits/stdc++.h>
using namespace std;
string s;
int n;
int k;
bool works(string a, string b) {
  bool foundLess = false;
  bool foundMore = false;
  for (int i = 0; i < n; i++) {
    if (a[i] - '0' > b[i] - '0') {
      return true;
    } else if (a[i] - '0' < b[i] - '0') {
      return false;
    }
  }
  return true;
}
int main() {
  cin >> n >> k;
  cin >> s;
  string temp = "";
  for (int i = 0; i < k; i++) {
    temp += s[i];
  }
  for (int i = k; i < n; i++) {
    temp += temp[i - k];
  }
  cout << n << endl;
  if (works(temp, s)) {
    cout << temp << endl;
  } else {
    int left = k;
    for (int i = k - 1; i >= 0; i--) {
      if (s[i] != '9') {
        left = i;
        break;
      }
    }
    temp = "";
    for (int i = 0; i < k; i++) {
      if (i < left) {
        temp += s[i];
      } else if (i == left) {
        temp += (s[i] + 1);
      } else {
        temp += ('0');
      }
    }
    for (int i = k; i < n; i++) {
      temp += temp[i - k];
    }
    cout << temp << endl;
  }
}
