#include <bits/stdc++.h>
using namespace std;
const long long M = 1e9 + 7;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxn = 1e5 + 5;
void solve() {
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  cout << n << endl;
  string t = s.substr(0, k);
  for (int i = k; i < n; i++) {
    t += t[i - k];
  }
  if (t >= s) {
    cout << t << endl;
  } else {
    for (int i = k - 1; i >= 0; i--) {
      if (t[i] < '9') {
        t[i]++;
        break;
      } else
        t[i] = '0';
    }
    for (int i = 0; i < k; i++) {
      for (int j = i; j < n; j += k) {
        t[j] = t[i];
      }
    }
    cout << t << endl;
  }
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) {
    solve();
  }
}
