#include <bits/stdc++.h>
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define RREP(i,a,b) for(int i=(a);i>=(b);i--)
#define pq priority_queue
#define P pair<int,int>
#define P2 pair<int,P>
#define P3 pair<int,P2>
typedef long long ll; typedef long double ld;
using namespace std;
const int INF=1e9, MOD=1e9+7, around[]={0,1,1,-1,-1,0,-1,1,0,0};
const ll LINF=1e18;
const ld PI=abs(acos(-1));
int n,m,a[100010],li[100010],li2[100010];

int main(){
	cin >> n >> m;
	REP(i,0,n) cin >> a[i],li[a[i]%m]++;
	sort(a,a+n);
	REP(i,0,n-1) if(a[i]==a[i+1]) i++,li2[a[i]%m]++;
	int pos=li[0]/2;
	REP(i,1,m/2+1){
		if(i==m-i){pos+=li[i]/2; continue;}
		int mi=min(li[i],li[m-i]);
		pos+=mi; li[i]-=mi; li[m-i]-=mi;
		pos+=min(li2[i],li[i]/2);
		pos+=min(li2[m-i],li[m-i]/2);
	}
	cout << pos << endl;
	return 0;
}
