#include <atcoder/all>
#include <algorithm>
#include <array>
#include <bitset>
#include <cmath>
#include <compare>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using ll=long long;
ll const mod = 998244353;
using mint = atcoder::modint998244353;

#define _REP_OVERLOAD(e1,e2,e3,_REP,...) _REP
#define _REP_2(i,x) for(ll i = 0; i < ll(x); i++)
#define _REP_3(i,x,y) for(ll i = ll(x); i < ll(y); i++)
#define rep(...) _REP_OVERLOAD(__VA_ARGS__, _REP_3, _REP_2)(__VA_ARGS__)

#define _IREP_OVERLOAD(e1,e2,e3,_IREP,...) _IREP
#define _IREP_2(i,x) for(ll i = ll(x); i > -1; i--)
#define _IREP_3(i,x,y) for(ll i = ll(x); i > ll(y); i--)
#define irep(...) _IREP_OVERLOAD(__VA_ARGS__, _IREP_3, _IREP_2)(__VA_ARGS__)

#define all(x) (x).begin(),(x).end()
#define vec vector
#define _V1_OVERLOAD(e1,e2,e3,e4,_V1,...) _V1
#define _V1_2(type,name) vec<type> name
#define _V1_3(type,name,n) vec<type> name(n)
#define _V1_4(type,name,n,val) vec<type> name(n,val)
#define v1(...) _V1_OVERLOAD(__VA_ARGS__, _V1_4, _V1_3, _V1_2)(__VA_ARGS__)

#define _V2_OVERLOAD(e1,e2,e3,e4,e5,_V2,...) _V2
#define _V2_2(type,name) vec<vec<type>> name
#define _V2_3(type,name,h) vec<vec<type>> name(h)
#define _V2_4(type,name,h,w) vec<vec<type>> name(h,vec<type>(w))
#define _V2_5(type,name,h,w,val) vec<vec<type>> name(h,vec<type>(w,val))
#define v2(...) _V2_OVERLOAD(__VA_ARGS__, _V2_5, _V2_4, _V2_3, _V2_2)(__VA_ARGS__)

// struct Pos{ll y,x; auto operator<=>(const Pos&) const = default;};
// struct dPos{double y,x; auto operator<=>(const dPos&) const = default;};
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
// const vec<Pos> Dir4={Pos(-1,0),Pos(1,0),Pos(0,-1),Pos(0,1)}; // UDLR
// const vec<Pos> Dir8={Pos(-1,0),Pos(1,0),Pos(0,-1),Pos(0,1),Pos(-1,-1),Pos(1,1),Pos(-1,1),Pos(1,-1)};
bool inRange(int lower, int val, int upper){return lower<=val && val<upper;}
// struct item{ll a; auto operator<=>(const item&) const = default;};

ll llinf=ll(1e18)*2+10;
double dinf=1e24;

int main()
{
    cout << fixed << setprecision(15);

    ll N,M;
    cin>>N>>M;
    v1(ll,A,N);
    rep(i,N) {
        cin>>A[i];
        A[i]--;}
    sort(all(A));

    unordered_set<ll> setA;
    rep(i,N){
        setA.insert(A[i]);
    }

    if(M%2){
        cout<<0<<'\n';
        return 0;
    }

    ll half=ll(M/2);

    ll res=0;
    for(auto ai:A){
        if(ai>=half) break;
        // if(setA.count(ai+half)&&setA.count(ai+quarter)) res++;
        // if(setA.count(ai+half)&&setA.count((ai+half+quarter)%M)) res++;
        if(setA.count(ai+half)) res+=N-2;

    }

    cout<<res<<'\n';

    return 0;

}