#include <bits/stdc++.h>
using namespace std;
string s, s1, orig;
long long n, k, minpos;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> k;
  cin >> s;
  minpos = n;
  for (int i = 0; i < k; i++) orig += s[i];
  bool ok = 1;
  s1 = s;
  for (int i = 0; i < n; i++) {
    if (i + k < n) s[i + k] = s[i];
  }
  if (s < s1) ok = 0;
  if (!ok) {
    s = s1;
    for (int i = k - 1; i >= 0; i--) {
      if (orig[i] != '9') {
        orig[i]++;
        for (int j = i + 1; j < k; j++) {
          orig[j] = '0';
        }
        break;
      }
    }
    for (int i = 0; i < n; i++) {
      s[i] = orig[i % k];
    }
    cout << s.size() << endl << s;
    cout << endl;
  } else {
    cout << s.size() << endl;
    cout << s << endl;
  }
}
