#include <bits/stdc++.h>
using namespace std;
double eps = 1e-9;
double pi = acos(-1);
long long fastpower(long long b, long long p) {
  long long ans = 1;
  while (p) {
    if (p % 2) {
      ans = (ans * b);
    }
    b = b * b;
    p /= 2;
  }
  return ans;
}
long long fastpowermod(long long b, long long p, long long m) {
  long long ans = 1;
  while (p) {
    if (p % 2) {
      ans = ((ans % m) * (b % m)) % m;
    }
    b = ((b % m) * (b % m)) % m;
    p /= 2;
  }
  return ans % m;
}
string makeitstring(long long n) {
  string ans;
  bool ch = 0;
  if (n < 0) {
    n *= -1;
    ch = 1;
  }
  if (n == 0) {
    ans = "0";
  };
  while (n) {
    long long mo = n % 10;
    mo += 48;
    char m = mo;
    ans = m + ans;
    n /= 10;
  }
  if (ch) {
    ans = '-' + ans;
  }
  return ans;
}
bool checksqrt(long long f) {
  long long num = sqrt(f);
  return (num * num == f);
}
bool compare(double f, double s) { return (abs(f - s) < eps); }
long long gcd(long long a, long long b) {
  while (b != 0) {
    long long a2 = a;
    a = b;
    b = a2 % b;
  }
  return a;
}
const int N = 1e6 + 1;
const int sz = 1e2 + 20;
long long cnt[sz];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  ;
  long long n, k;
  cin >> n >> k;
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    long long x;
    cin >> x;
    long long now = x % k;
    if (cnt[(k - now) % k]) {
      ans++;
      cnt[(k - now) % k]--;
    } else {
      cnt[now]++;
    }
  }
  cout << ans * 2;
  return 0;
}
