#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<ll, int>;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, k;
  cin >> n >> k;
  vector<int> X(n), a(n), b(n);
  for (__typeof(n - 1) i = 0; i <= n - 1; i++) {
    char x;
    cin >> x;
    X[i] = int(x - '0');
  }
  for (__typeof(n - 1) i = 0; i <= n - 1; i++) {
    a[i] = X[i % k];
    b[i] = X[i % k];
  }
  for (int i = k - 1; i >= 0; i--) {
    b[i]++;
    if (b[i] == 10) {
      b[i] = 0;
    } else
      break;
  }
  for (__typeof(n - 1) i = k; i <= n - 1; i++) {
    b[i] = b[i % k];
  }
  if (a >= X) {
    cerr << "'a'"
            ": "
         << ('a') << "\t";
    cout << a.size() << "\n";
    for (auto c : a) cout << c;
  } else {
    cout << b.size() << "\n";
    for (auto c : b) cout << c;
  }
}
