#include <bits/stdc++.h>
using namespace std;
const int M = 1e9 + 7;
long long int n, k;
string s, s1;
void hi() {
  for (int i = k; i < s.length(); i++) {
    s[i] = s[i - k];
  }
}
int main() {
  cout.precision(10);
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> k >> s;
  s1 = s;
  hi();
  if (s >= s1) {
    cout << n << endl;
    cout << s;
  } else {
    bool ok = true;
    int i = k - 1;
    if (s[i] != '9') {
      s[i] = s[i] + 1;
      hi();
      cout << n << endl;
      cout << s;
    } else {
      s[i] = '0';
      for (int j = i - 1; j >= 0; j--) {
        if (s[j] != '9') {
          s[j]++;
          ok = false;
          hi();
          cout << n << endl;
          cout << s;
          break;
        } else {
          s[j] = '0';
        }
      }
      if (ok) {
        cout << n + 1 << endl;
        cout << s1[0] + 1;
        for (int i = 0; i < n; i++) {
          cout << "0";
        }
      }
    }
  }
  return 0;
}
long long int nChooseR(long long int n, long long int k) {
  if (k > n) return 0;
  if (k * 2 > n) k = n - k;
  if (k == 0) return 1;
  long long int result = n;
  for (int i = 2; i <= k; ++i) {
    result *= (n - i + 1);
    result /= i;
  }
  return result;
}
long long int power(long long int a, long long int b) {
  if (b == 1) {
    return a % M;
  } else {
    if (b % 2 == 0)
      return (power(a, b / 2) % M * power(a, b / 2) % M) % M;
    else
      return (((power(a, b / 2) % M * power(a, b / 2) % M) % M) * a % M) % M;
  }
}
