#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int n, k;
string s;
vector<int> no, good;
bool greate(vector<int> v1, vector<int> v2) {
  for (int i = 0; i <= n - 1; i++) {
    if (v1[i] > v2[i]) return true;
    if (v1[i] < v2[i]) return false;
  }
  return true;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n >> k;
  cin >> s;
  for (int i = 0; i <= n - 1; i++) {
    no.push_back(s[i] - '0');
    good.push_back(s[i % k] - '0');
  }
  if (greate(good, no)) {
    cout << good.size();
    cout << "\n";
    for (__typeof(good.begin()) it = good.begin(); it != good.end(); it++) {
      cout << *it;
    }
    return 0;
  }
  int ptr = k - 1;
  good[ptr]++;
  while (1) {
    if (ptr == 0) break;
    if (good[ptr] <= 9) break;
    good[ptr] = good[ptr] % 10;
    ptr--;
    good[ptr]++;
  }
  for (int i = 0; i <= n - 1; i++) good[i] = good[i % k];
  cout << good.size();
  cout << "\n";
  for (__typeof(good.begin()) it = good.begin(); it != good.end(); it++) {
    cout << *it;
  }
  return 0;
}
