#include <bits/stdc++.h>
const long long SZ = 401010;
const long long INF = 1e18;
const long long MOD = 1000000007;
const long long mod = 998244353;
long long opnmbr = 1;
using namespace std;
void solve() {}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long lcm(long long a, long long b) { return (a / gcd(a, b)) * b; }
bool isPrime(long long n) {
  long long sq = sqrt(n);
  for (long long i = 2; i <= sq; i++) {
    if (n % i == 0) {
      return false;
    }
  }
  return true;
}
void krdiyasuru() {
  long long n, k;
  cin >> n >> k;
  string a;
  cin >> a;
  string chk;
  chk = a;
  for (long long i = k; i < (n); i++) {
    a[i] = a[i - k];
  }
  if (a >= chk) {
    cout << n << '\n';
    cout << a << '\n';
    return;
  }
  for (long long i = k - 1; i >= (0); i--) {
    if (a[i] == '9' && i != 0) {
      a[i] = '0';
    } else if (a[i] != '9') {
      a[i]++;
      break;
    }
  }
  cout << n << '\n';
  for (long long i = k; i < (n); i++) {
    a[i] = a[i - k];
  }
  cout << a << '\n';
  return;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  { krdiyasuru(); }
  return 0;
}
