#include <bits/stdc++.h>
using namespace std;
template <class T, class U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}
template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  os << "{";
  for (int i = 0; i < (int)v.size(); i++) {
    if (i) os << ", ";
    os << v[i];
  }
  os << "}";
  return os;
}
template <typename Arg1>
void __f(const char* name, Arg1&& arg1) {
  cerr << name << " : " << arg1 << std::endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args) {
  const char* comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
const int N = 200005;
char s[N];
int a[N], b[N];
int main() {
  int n, k;
  scanf("%d", &(n));
  scanf("%d", &(k));
  scanf("%s", s);
  for (int i = 1; i <= n; i++) a[i] = s[i - 1] - '0';
  for (int i = 1; i <= k; i++) b[i] = a[i];
  for (int i = k + 1; i <= n; i++) b[i] = b[i - k];
  int ok = 1;
  for (int i = 1; i <= n; i++) {
    if (a[i] > b[i]) {
      ok = 0;
      break;
    }
    if (b[i] > a[i]) break;
  }
  if (ok) {
    printf("%d\n", n);
    for (int i = 1; i <= n; i++) printf("%d", b[i]);
    return 0;
  }
  if (b[k] == 9) {
    for (int j = k; j >= 1; j--) {
      if (b[j] == 9)
        b[j] = 0;
      else {
        b[j]++;
        break;
      }
    }
  } else
    b[k]++;
  for (int i = k + 1; i <= n; i++) b[i] = b[i - k];
  printf("%d\n", n);
  for (int i = 1; i <= n; i++) printf("%d", b[i]);
  return 0;
}
