#include <bits/stdc++.h>
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
signed main() {
  long long int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  string ns = s;
  for (long long int i = 0; i < k; i++) {
    char dig = s[i];
    for (long long int j = i; j < n; j += k) ns[j] = dig;
  }
  if (ns >= s) {
    cout << ns.size() << "\n" << ns << "\n";
  } else {
    for (long long int i = k - 1; i >= 0; i--) {
      char dig = ns[i];
      if (dig == '9') {
        for (long long int j = i; j < n; j += k) ns[j] = '0';
      } else {
        for (long long int j = i; j < n; j += k) ns[j] = (char)(dig + 1);
        cout << ns.size() << "\n" << ns << "\n";
        return 0;
      }
    }
    string nns = "1" + ns;
    for (long long int i = 0; i < nns.size(); i += k) nns[i] = '1';
    cout << nns.size() << "\n" << nns << "\n";
  }
  return 0;
}
