#include <bits/stdc++.h>
using namespace std;
const int N = int(1e4 + 5);
const int INF = int(1e9);
const int MOD = int(1e9 + 9);
bool cmp(deque<char> x, deque<char> y) {
  if (x.size() > y.size()) return true;
  if (x.size() < y.size()) return false;
  for (int i = 0; i < x.size(); i++) {
    if (x[i] > y[i]) return true;
    if (x[i] < y[i]) return false;
  }
  return true;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, k;
  cin >> n >> k;
  deque<char> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  deque<char> b, c;
  for (int i = 0; i < k; i++) {
    b.emplace_back(a[i]);
    c.emplace_back(a[i]);
  }
  while (b.size() < a.size()) {
    b.push_back(b[b.size() - k]);
  }
  if (cmp(b, a)) {
    cout << b.size() << '\n';
    for (auto i : b) cout << i;
    return 0;
  }
  int r = c.size() - 1;
  while (r >= 0 && c[r] == '9') {
    c[r] = '0';
    r--;
  }
  if (r == -1)
    c.push_front('1');
  else
    c[r]++;
  while (c.size() < a.size()) {
    c.push_back(c[c.size() - k]);
  }
  cout << c.size() << '\n';
  for (auto i : c) cout << i;
  return 0;
}
