#include <bits/stdc++.h>
using namespace std;
long long powmod(long long base, long long exponent, long long mod) {
  long long ans = 1;
  while (exponent) {
    if (exponent & 1) ans = (ans * base) % mod;
    base = (base * base) % mod;
    exponent /= 2;
  }
  return ans;
}
long long gcd(long long a, long long b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
const int upperlimit = 1e6 + 100;
const int mod = 1e9 + 7;
void plusone(string &s) {
  for (int i = s.size() - 1; i >= 0; i--) {
    if (s[i] != '9') {
      s[i]++;
      break;
    } else
      s[i] = '0';
  }
}
bool cmp(string a, string b) {
  for (int i = 0; i < a.size(); i++) {
    int j = i;
    j %= b.size();
    if (a[i] > b[j]) return false;
    if (a[i] < b[j]) return true;
  }
  return true;
}
int main() {
  string s, c;
  int n, k;
  cin >> n >> k >> s;
  c.append(s, 0, min(n, k));
  if (!cmp(s, c)) plusone(c);
  cout << n << "\n";
  for (int i = 0; i < n; i++) cout << c[i % k];
  return 0;
}
