#include <bits/stdc++.h>
long long gi() {
  long long x = 0, f = 1;
  char ch = getchar();
  while (!isdigit(ch)) f ^= ch == '-', ch = getchar();
  while (isdigit(ch)) x = x * 10 + ch - '0', ch = getchar();
  return f ? x : -x;
}
char S[300010], ans[300010];
int main() {
  int n = gi(), k = gi();
  scanf("%s", S + 1);
  for (int i = 1; i <= n; ++i) ans[i] = S[(i - 1) % k + 1];
  for (int i = 1; i <= n; ++i)
    if (S[i] > ans[i]) {
      ++ans[k];
      for (int j = k; j; --j)
        if (ans[j] == '9' + 1)
          ans[j] = '0', ans[j - 1]++;
        else
          break;
      for (int j = k + 1; j <= n; ++j) ans[j] = ans[j - k];
      break;
    } else if (S[i] < ans[i])
      break;
  printf("%d\n%s\n", n, ans + 1);
  return 0;
}
