#include <bits/stdc++.h>
using namespace std;
bool cmp(pair<int, int> a, pair<int, int> b) {
  if (a.first == b.first) return a.second > b.second;
  return a.first < b.first;
}
int findS(int s) {
  int l = 1, r = (s / 2) + 1;
  while (l <= r) {
    int mid = (l + r) / 2;
    int sum = mid * (mid + 1) / 2;
    if (sum == s)
      return mid;
    else if (sum > s)
      r = mid - 1;
    else
      l = mid + 1;
  }
  return -1;
}
int leftone(int a[], int k, int j) {
  int i;
  for (i = k - 1; i >= 0; i--) {
    if (j == 1)
      if (a[i] == 2)
        return i;
      else if (a[i] == 1)
        return i;
  }
  return -1;
}
int rightone(int a[], int l, int j, int n) {
  int i;
  for (i = l; i < n - 1; i++) {
    if (j == 1)
      if (a[i] == 2)
        return i;
      else if (a[i] == 1)
        return i;
  }
  return -1;
}
int main() {
  int n, k, i;
  string s, ans = "";
  cin >> n >> k >> s;
  for (i = 0; i < n; i++) ans += s[i % k];
  if (ans < s)
    for (i = k - 1; ++s[i] > '9'; i--) s[i] = '0';
  for (i = 0; i < n; i++) ans[i] = s[i % k];
  cout << n << "\n" << ans;
  return 0;
}
