#include <bits/stdc++.h>
using namespace std;
bool isprime(long long a) {
  for (long long i = 2; i <= pow(a, 0.5); ++i) {
    if (a % i == 0) {
      return false;
    }
  }
  return true;
}
long long ceil(long long a, long long b) {
  long long c = (a + b - 1) / b;
  return c;
}
long long gcd(long long a, long long b) {
  if (a == 0) {
    return b;
  }
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}
long long power_mod(long long a, long long b) {
  if (b == 0) {
    return 1;
  }
  long long temp = power_mod(a, b / 2);
  temp = (temp * temp) % 1000000007;
  if (b % 2) {
    temp = (temp * a) % 1000000007;
  }
  return temp;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int t = 1;
  while (t--) {
    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;
    string p = "";
    p = s.substr(0, k);
    for (int i = k; i < n; i++) {
      p += p[i - k];
    }
    cout << n << "\n";
    if (p >= s) {
      cout << p << "\n";
      continue;
    }
    for (int i = k - 1; i >= 0; --i) {
      if (p[i] == '9') {
        p[i] = '0';
      } else {
        p[i]++;
        break;
      }
    }
    for (int i = k; i < n; ++i) {
      p[i] = p[i - k];
    }
    cout << p << "\n";
  }
}
