#include <bits/stdc++.h>
using namespace std;
template <typename Tp>
inline void outarr(Tp _begin, Tp _end, const char* _delim = " ") {
  for (Tp current = _begin; current != _end; ++current) {
    std::cout << *current << _delim;
  }
  std::cout << '\n';
}
using ll = long long;
using pii = std::pair<int, int>;
constexpr int INF = 0x3f3f3f3f;
constexpr int MOD = static_cast<const int>(1e9 + 7);
bool used[200000];
int main() {
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int n, k;
  string s;
  cin >> n >> k >> s;
  auto pref = s.substr(0, k);
  string ans = pref;
  for (int i = 0; i < (n - k); ++i) {
    ans += ans[i];
  }
  if (ans >= s) {
    cout << n << "\n";
    return cout << (ans) << '\n', 0;
    ;
  }
  for (int i = k - 1; i >= 0; --i) {
    if (pref[i] == '9') {
      pref[i] = '0';
    } else {
      ++pref[i];
      break;
    }
  }
  ans = pref;
  for (int i = 0; i < (n - k); ++i) {
    ans += ans[i];
  }
  cout << n << "\n";
  cout << ans << "\n";
  return 0;
}
