#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int N = 200200;
char s[N];
char p[N];
int n, k;
int main() {
  scanf("%d%d", &n, &k);
  scanf("%s", s);
  for (int i = 0; i < n; i++) {
    if (i < k)
      p[i] = s[i];
    else
      p[i] = p[i - k];
  }
  bool ok = true;
  for (int i = 0; i < n; i++) {
    if (s[i] == p[i]) continue;
    ok = s[i] < p[i];
    break;
  }
  if (ok) {
    p[n] = '\0';
    printf("%d\n%s\n", n, p);
    return 0;
  }
  int pos = k - 1;
  while (pos >= 0 && p[pos] == '9') {
    p[pos] = '0';
    pos--;
  }
  if (pos < 0) {
  } else {
    p[pos]++;
    for (int i = k; i < n; i++) p[i] = p[i - k];
    p[n] = '\0';
    printf("%d\n%s\n", n, p);
    return 0;
  }
  printf("%d\n", n + 1);
  for (int i = 0; i < k; i++) printf("%d", (i % k == 0 ? 1 : 0));
  printf("\n");
  return 0;
}
