#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void jpg() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
long long mpow(long long base, long long exp);
int32_t main() {
  jpg();
  long long n, k;
  cin >> n >> k;
  string a;
  cin >> a;
  string b = a;
  for (long long i = k; i < n; i++) b[i] = a[i % k];
  if (b >= a)
    cout << n << "\n" << b << "\n";
  else {
    for (long long i = k - 1; i >= 0; i--)
      if (b[i] == '9')
        b[i] = '0';
      else {
        b[i] = b[i] + 1;
        break;
      }
    for (long long i = k; i < n; i++) b[i] = b[i % k];
    cout << n << "\n" << b << "\n";
  }
}
long long mpow(long long base, long long exp) {
  base %= 998244353;
  long long result = 1;
  while (exp > 0) {
    if (exp & 1) result = ((long long)result * base) % 998244353;
    base = ((long long)base * base) % 998244353;
    exp >>= 1;
  }
  return result;
}
