import std.stdio, std.conv, std.string, std.array, std.range, std.algorithm, std.container;
import std.math, std.random, std.bigint, std.datetime, std.format;
void main(string[] args){ if(args.length > 1) if(args[1] == "-debug") DEBUG = 1; solve(); }
void log()(){ writeln(""); } void log(T, A ...)(T t, lazy A a){ if(DEBUG) write(t, " "), log(a); } bool DEBUG = 0; 
string read(){ static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res; }
T read(T)(){ return read.to!T; }
T[] read(T)(long n){ return n.iota.map!(_ => read!T).array; }
T[][] read(T)(long m, long n){ return m.iota.map!(_ => read!T(n)).array; }
// ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- //

void solve(){
	
	int n = read.to!int;
	int m = read.to!int;
	
	long[] xs;
	foreach(i; 0 .. n) xs ~= read.to!long;
	
	int[long] xcnt;
	foreach(x; xs){
		if(x !in xcnt) xcnt[x] = 0;
		xcnt[x] += 1;
	}
	
	int[] as, bs; // a: 同じ数のペアの個数 b: 全個数
	as = new int[](m);
	bs = new int[](m);
	long[] ks = xcnt.keys;
	foreach(x; ks){
		int k = x % m;
		as[k] += xcnt[x] / 2;
		bs[k] += xcnt[x];
	}
	
	long ans;
	foreach(k; 0 .. m){
		if(m - k < k) continue;
		if(k == 0) ans += bs[k] / 2;
		else if(k + k == m) ans += bs[k] / 2;
		else{
			if(bs[k] >= bs[m - k]){
				ans += bs[m - k];
				ans += min((bs[k] - bs[m - k]) / 2, as[k]);
			}
			else{
				ans += bs[k];
				ans += min((bs[m - k] - bs[k]) / 2, as[m - k]);
			}
		}
	}
	
	ans.writeln;
	
}