#include <bits/stdc++.h>
using namespace std;
const long long inf = 4e18;
const long long N = 2e5 + 10;
void testCase() {
  long long n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  string t = s.substr(0, k);
  long long part = n / k;
  long long rem = n % k;
  string ans;
  for (long long i = 0; i < part; i++) ans += t;
  ans += t.substr(0, rem);
  cout << n << '\n';
  if (ans >= s) {
    cout << ans;
    return;
  }
  long long add = 1, carry = 0;
  reverse(begin(t), end(t));
  for (long long i = 0; i < k; i++) {
    long long d = t[i] - '0';
    d += add + carry;
    carry = d / 10;
    d %= 10;
    t[i] = d + '0';
    add = 0;
  }
  if (carry) t.push_back(char(carry + '0'));
  reverse(begin(t), end(t));
  ans = "";
  for (long long i = 0; i < part; i++) ans += t;
  ans += t.substr(0, rem);
  cout << ans;
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr), cout.tie(nullptr);
  long long t_c = 1;
  while (t_c--) testCase();
}
