#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
const long long infLL = 0x3f3f3f3f3f3f3f3fLL;
const int maxn = 200000 + 5;
string extend(string s, int n) {
  string ret;
  while (ret.length() + s.length() <= n) ret += s;
  ret += s.substr(0, n - ret.length());
  return ret;
}
int main() {
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  string pre = s.substr(0, k);
  string ret = extend(pre, s.length());
  cout << n << endl;
  if (ret >= s) {
    cout << ret << endl;
  } else {
    for (int i = pre.length() - 1; i >= 0; --i) {
      if (pre[i] != '9') {
        ++pre[i];
        break;
      }
      pre[i] = '0';
    }
    cout << extend(pre, s.length()) << endl;
  }
  return 0;
}
