#include /* #include #include namespace mp = boost::multiprecision; using bint = mp::cpp_int; */ #include #define rep(i,n) for (int i = 0; i < int(n); ++i) #define repp(i,n,m) for (int i = m; i < int(n); ++i) #define repb(i,n) for (int i = int(n)-1; i >= 0; --i) #define endl "\n" using namespace std; using namespace atcoder; using ll = long long; using ld = long double; using P = pair; using PL = pair; using pdd = pair; using pil = pair; using pli = pair; using ppi = pair; using pip = pair; const int INF = 1001001007; const long long mod1 = 1000000007LL; const long long mod2 = 998244353LL; const ll inf = 2e18; const ld pi = 3.14159265358979323; const ld eps = 1e-7; const char _ = ' '; templatevoid o(T a); templateistream &operator>>(istream &is,vector &v){for(auto &e:v)is>>e;return is;} templateostream &operator<<(ostream &os,const vector &v){if(v.size()!=0){rep(i,v.size())os<istream &operator>>(istream &is,vector> &v){for(auto &e:v)is>>e;return is;} templateostream &operator<<(ostream &os,const vector> &v){if(v.size()!=0){for(auto &e:v)o(e);}return os;} templatebool range(T a,T b,T x){return (a<=x&&xbool rrange(T a,T b,T c,T d,T x,T y){return (range(a,c,x)&&range(b,d,y));} templatevoid rev(vector &v){reverse(v.begin(),v.end());} void revs(string &s) {reverse(s.begin(),s.end());} templatevoid sor(vector &v, int f=0){sort(v.begin(),v.end());if(f!=0) rev(v);} templatebool chmin(T &a,const T &b){if(a>b){a=b;return true;}return false;} templatebool chmax(T &a,const T &b){if(avoid eru(vector &v){sor(v);v.erase(unique(v.begin(),v.end()),v.end());} templateT cel(T a,T b){if(a%b==0)return a/b;return a/b +1;} void o(){cout<<"!?"<void o(T a){cout<void mout(T a){cout< void print(const T& a){ cout << a; } int out(){ putchar('\n'); return 0; } template int out(const T& t){ print(t); putchar('\n'); return 0; } template int out(const Head& head, const Tail&... tail){ print(head); putchar(' '); out(tail...); return 0; } void yes(){cout << "Yes" << endl;} void no (){cout << "No" << endl;} void yn (bool t){if(t)yes();else no();} templatevoid dame(bool t, T s){if(!t){cout << s << endl;exit(0);}} void fast_io(){cin.tie(0); ios::sync_with_stdio(0); cout<void o2(pair a){out(a.first,a.second);} vector dx = {0,1,0,-1,1,1,-1,-1}; vector dy = {1,0,-1,0,1,-1,-1,1}; const string ALP = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; const string alp = "abcdefghijklmnopqrstuvwxyz"; const string NUM = "0123456789"; ll gcd(ll a,ll b){return b?gcd(b,a%b):a;} ll lcm(ll a,ll b){return a/gcd(a,b)*b;} ll mpow(ll x,ll n,ll m){if(n==0)return 1LL;x%=m;ll a=mpow(x,n/2,m);a=a*a%m;return (n&1)?a*x%m:a;} template ll tentou(vector ar){ int n = ar.size(); set st; rep(i,n) st.insert(ar[i]); map mp; int ind = 0; for (T x : st){ mp[x] = ind; ind++; } fenwick_tree fw(ind); ll ans = 0; rep(i,n){ int a = mp[ar[i]]; ans += i - fw.sum(0,a+1); fw.add(a,1); } return ans; } struct edge{ int from, to; long long cost; edge(int _from = -1, int _to = -1, long long _cost = 1LL) : from(_from), to(_to), cost(_cost) {} }; struct vertex{ vector adj; }; struct Graph{ int n; vector vs; void add_edge(int from, int to, long long cost = 1LL){ assert(0 <= from && from < n); assert(0 <= to && to < n); vs[from].adj.emplace_back(edge(from,to,cost)); } void add_dual_edge(int from, int to, long long cost = 1LL){ assert(0 <= from && from < n); assert(0 <= to && to < n); vs[from].adj.emplace_back(edge(from,to,cost)); vs[to].adj.emplace_back(edge(to,from,cost)); } Graph(int _n) : n(_n) , vs(n) {} vector dijkstra(int s){ using pli = pair; priority_queue, greater> pque; vector dist(n,inf); dist[s] = 0LL; pque.push(pli(0,s)); while (!pque.empty()){ pli p = pque.top(); pque.pop(); if (dist[p.second] < p.first) continue; for (edge x : vs[p.second].adj){ if (dist[x.to] > p.first + x.cost){ dist[x.to] = p.first + x.cost; pque.push(pli(dist[x.to],x.to)); } } } return dist; } vector bfs01(int s){ deque que; vector dist(n,inf); dist[s] = 0LL; que.push_front(s); while (!que.empty()){ int p = que.front(); que.pop_front(); for (edge x : vs[p].adj){ if (dist[x.to] > dist[p] + x.cost){ dist[x.to] = dist[p] + x.cost; if (x.cost == 0LL) que.push_front(x.to); else que.push_back(x.to); } } } return dist; } vector dfs(int s){ vector ans; vector vis(n,0); _dfs(s,ans,vis); return ans; } private: void _dfs(int s, vector &ans, vector &vis){ vis[s]++; for (edge x : vs[s].adj){ if (vis[x.to] == 0){ _dfs(x.to,ans,vis); } } ans.emplace_back(s); } }; struct Tree{ Tree(int _n, int _root = 0) : n(_n), root(_root) { assert(0 <= root && root < n); initialize(); } void add_edge(int from, int to, long long cost = 1LL){ assert(0 <= from && from < n); assert(0 <= to && to < n); vs[from].adj.emplace_back(edge(from,to,cost)); } void add_dual_edge(int from, int to, long long cost = 1LL){ assert(0 <= from && from < n); assert(0 <= to && to < n); vs[from].adj.emplace_back(edge(from,to,cost)); vs[to].adj.emplace_back(edge(to,from,cost)); } int size(){return n;} int parent(int v){ assert(0 <= v && v < n); if (is_done_par_rdist_init == false) par_rdist_init(); return par[v]; } int depth(int v){ assert(0 <= v && v < n); if (dep[v] != -1) return dep[v]; if (v == root) return dep[v] = 0; return dep[v] = depth(parent(v)) + 1; } int subtree_size(int v){ assert(0 <= v && v < n); if (sub[v] != 0) return sub[v]; sub[v] = 1; for (edge x : vs[v].adj){ if (x.to != parent(v)) sub[v] += subtree_size(x.to); } return sub[v]; } int lca(int u, int v){ assert(0 <= u && u < n); assert(0 <= v && v < n); if (is_done_lca_init == false) lca_init(); if (depth(u) > depth(v)) swap(u,v); for (int i = 0; i < 30; i++) if ((depth(v) - depth(u)) >> i & 1) v = par2[i][v]; if (u == v) return u; for (int k = 29; k >= 0; k--){ if (par2[k][u] != par2[k][v]) { u = par2[k][u]; v = par2[k][v]; } } return par2[0][u]; } long long dist(int u, int v){ assert(0 <= u && u < n); assert(0 <= v && v < n); if (is_done_par_rdist_init == false) par_rdist_init(); return rdist[u] + rdist[v] - rdist[lca(u,v)] * 2LL; } vector path(int f, int t){ assert(0 <= f && f < n); assert(0 <= t && t < n); int v = lca(f,t); vector fp = {f}; vector tp = {t}; int fn = f, tn = t; while (fn != v){ fn = parent(fn); fp.emplace_back(fn); } while (tn != v){ tn = parent(tn); tp.emplace_back(tn); } for (int i = int(tp.size()) - 2; i >= 0; i--){ fp.emplace_back(tp[i]); } return fp; } vector alldists(int v){ assert(0 <= v && v < n); if (v == 0) return rdist; vector dists(n,1e18); vector vis(n,0); dists[v] = 0LL; queue que; que.push(v); while (!que.empty()){ int p = que.front(); que.pop(); vis[p]++; for (edge x : vs[p].adj){ if (vis[x.to] == 0){ dists[x.to] = dists[p] + x.cost; que.push(x.to); } } } return dists; } vector dfs(int v){ assert(0 <= v && v < n); vector ans; vector vis(n,0); _dfs(v,vis,ans); return ans; } vector vs; private: int n; int root; bool is_done_lca_init; bool is_done_par_rdist_init; vector par; vector dep; vector sub; vector rdist; vector> par2; void initialize(){ is_done_lca_init = false; is_done_par_rdist_init = false; vs.resize(n); dep.resize(n,-1); sub.resize(n,0); } void lca_init(){ par2.resize(30,vector(n,-1)); for (int i = 0; i < n; i++) par2[0][i] = parent(i); for (int i = 0; i < 29 ; i++) { for (int j = 0; j < n; j++) { if (par2[i][j] < 0) par2[i+1][j] = -1; else par2[i+1][j] = par2[i][par2[i][j]]; } } is_done_lca_init = true; } void par_rdist_init(){ par.resize(n,-2); rdist.resize(n,-1); par[root] = -1; rdist[root] = 0; queue que; que.push(root); while (!que.empty()){ int p = que.front(); que.pop(); for (edge x : vs[p].adj){ if (par[x.to] == -2){ par[x.to] = p; rdist[x.to] = rdist[p] + x.cost; que.push(x.to); } } } is_done_par_rdist_init = true; } void _dfs(int v, vector &vis, vector &ans){ vis[v]++; for (edge x : vs[v].adj){ if (vis[x.to] == 0) _dfs(x.to,vis,ans); } ans.emplace_back(v); } }; template struct doubling{ vector vec; doubling (vector _vec) : vec(_vec) {} map mp; ll length_of_loop = -1; ll top_of_loop = -1; void init(){ ll ind = 0; for (T x : vec){ if (mp.find(x) == mp.end()) mp[x] = ind, ind++; else { length_of_loop = ind - mp[x]; top_of_loop = mp[x]; break; } } } ll len(){ if (length_of_loop == -1) init(); return length_of_loop; } ll top(){ if (top_of_loop == -1) init(); return top_of_loop; } T get(ll n){ assert(0 <= n); if (n < top()) return vec[n]; ll d = n - top(); return vec[top() + (d % len())]; } }; struct Mo{ vector left, right, order, v; int width, nl, nr, ptr; Mo (int n = 0) : width(sqrt(n)), nl(0), nr(0), ptr(0), left(0), right(0), v(n,-1) {} void insert(int l, int r){ // [l,r) left.emplace_back(l); right.emplace_back(r); } void build(){ // sort all query order.resize(left.size()); iota(order.begin(),order.end(),0); sort(order.begin(),order.end(),[&](int a, int b){ if(left[a] / width != left[b] / width) return left[a] < left[b]; return right[a] < right[b]; }); } int process(){ // do 1 query if (ptr == int(order.size())) return -1; const int id = order[ptr]; while (nl > left[id]) distribute(--nl); while (nl < left[id]) distribute(nl++); while (nr > right[id]) distribute(--nr); while (nr < right[id]) distribute(nr++); return order[ptr++]; } inline void distribute(int idx){ // x x x (nl) o o o (nr) x x ... v[idx] *= -1; if (v[idx] == 1) add(idx); else del(idx); } void add(int idx); void del(int idx); }; template struct Matrix{ int rows; int cols; vector> m; Matrix (int h = 0, int w = 0, T init = T(0)) : m(h,vector(w,init)), rows(h), cols(w){} Matrix (vector> _init) : m(_init), rows(_init.size()), cols(_init.at(0).size()){} vector operator[](const int i) const {return m[i];} vector& operator[](const int i) {return m[i];} Matrix &operator+= (const Matrix &r){ assert(this->rows == r.rows && this->cols == r.cols); for (int i = 0; i < r.rows; ++i){ for (int j = 0; j < r.cols; ++j){ m[i][j] += r.m[i][j]; } } return *this; } Matrix &operator-= (const Matrix &r){ assert(this->rows == r.rows && this->cols == r.cols); for (int i = 0; i < r.rows; ++i){ for (int j = 0; j < r.cols; ++j){ m[i][j] -= r.m[i][j]; } } return *this; } Matrix &operator*= (const Matrix &r){ assert(this->cols == r.rows); Matrix res(rows, r.cols); for (int i = 0; i < rows; ++i){ for (int j = 0; j < r.cols; ++j){ for (int k = 0; k < r.rows; ++k){ res[i][j] += m[i][k] * r.m[k][j]; } } } return *this = res; } Matrix operator+ (const Matrix &r) const {return Matrix(*this) += r;} Matrix operator- (const Matrix &r) const {return Matrix(*this) -= r;} Matrix operator* (const Matrix &r) const {return Matrix(*this) *= r;} bool operator== (const Matrix &r){ if (rows != r.rows || cols != r.cols) return false; for (int i = 0; i < r.rows; ++i){ for (int j = 0; j < r.cols; ++j){ if (m[i][j] != r.m[i][j]) return false; } } return true; } Matrix& operator+=(const T &r){ for (int i = 0; i < rows; ++i){ for (int j = 0; j < cols; ++j){ m[i][j] += r; } } return *this; } Matrix& operator-=(const T &r){ for (int i = 0; i < rows; ++i){ for (int j = 0; j < cols; ++j){ m[i][j] -= r; } } return *this; } Matrix& operator*=(const T &r){ for (int i = 0; i < rows; ++i){ for (int j = 0; j < cols; ++j){ m[i][j] *= r; } } return *this; } Matrix& operator/=(const T &r){ for (int i = 0; i < rows; ++i){ for (int j = 0; j < cols; ++j){ m[i][j] /= r; } } return *this; } Matrix operator+ (const T &r) const {return Matrix(*this) += r;} Matrix operator- (const T &r) const {return Matrix(*this) -= r;} Matrix operator* (const T &r) const {return Matrix(*this) *= r;} Matrix operator/ (const T &r) const {return Matrix(*this) /= r;} Matrix e(){ assert(this->rows == this->cols); Matrix res(this->rows, this->rows); for (int i = 0; i < rows; ++i) res[i][i] = 1; return res; } Matrix matpow(ll n){ assert(this->rows == this->cols); if (n == 0) return e(); Matrix f = matpow(n / 2); Matrix ans = f * f; if (n % 2 == 1) ans *= *this; return ans; } // for T = int, long long, double, long double void show(){ for (int i = 0; i < rows; ++i){ for (int j = 0; j < cols; ++j){ cout << m[i][j] << (j+1 == this->cols ? "\n" : " "); } } } }; template struct Rui{ /* - op(e,x) = op(x,e) = x - op(l,opinv(l,lr)) = lr */ int n; vector vec, lrui, rrui; Rui (vector _vec) : n(int(_vec.size())), vec(_vec) { lrui.resize(n+1), rrui.resize(n+1); lrui[0] = rrui[n] = e(); for (int i = 0; i < n; i++) lrui[i+1] = op(lrui[i],vec[i]); for (int i = n; i > 0; i--) rrui[i-1] = op(rrui[i],vec[i-1]); } template S prod(int l, int r = -1){ // [l,r) if (r == -1) return vec[l]; return opinv(lrui[l],lrui[r]); } S nprod(int l, int r = -1){ // [0,l) * [r,n) if (r == -1) r = l+1; return op(lrui[l],rrui[r]); } }; struct MINT998244353{ using mint = modint998244353; vector kaijo, kainv; int N; MINT998244353 (int lim = 200000) : N(lim), kaijo(lim+1,1), kainv(lim+1,1) { rep(i,N) kaijo[i+1] = kaijo[i] * (i+1); rep(i,N) kainv[i+1] = kainv[i] / (i+1); } mint factrial(int x){return kaijo[x];} mint inv_factorial(int x){return kainv[x];} mint ncr(int n, int r){return kaijo[n] * kainv[r] * kainv[n-r];} template vector beki(T r, int n = -1){ if (n == -1) n = N; vector res(n+1,1); rep(i,n) res[i+1] = res[i] * mint(r); return res; } vector vec_inv(vector &a){ vector res(a.size()); rep(i,int(a.size())) res[i] = a[i].inv(); return res; } }; struct MINT1000000007{ using mint = modint1000000007; vector kaijo, kainv; int N; MINT1000000007 (int lim = 200000) : N(lim), kaijo(lim+1,1), kainv(lim+1,1) { rep(i,N) kaijo[i+1] = kaijo[i] * (i+1); rep(i,N) kainv[i+1] = kainv[i] / (i+1); } mint factrial(int x){return kaijo[x];} mint inv_factorial(int x){return kainv[x];} mint ncr(int n, int r){ if (n < r) return mint(0); return kaijo[n] * kainv[r] * kainv[n-r]; } template vector beki(T r, int n = -1){ if (n == -1) n = N; vector res(n+1,1); rep(i,n) res[i+1] = res[i] * mint(r); return res; } vector vec_inv(vector &a){ vector res(a.size()); rep(i,int(a.size())) res[i] = a[i].inv(); return res; } }; ll op(ll a, ll b){ if (a == -1) return b; if (b == -1) return a; return gcd(a,b); } ll e(){return -1;} ll opinv(int a, int ab){return ab - a;} template void vmint(vector &v){ int n = v.size(); if (n == 0) { cout << endl; return ; } rep(i,n) cout << v[i].val() << (i < n-1 ? " " : "\n"); } template void vvmint(vector> &v){ int n = v.size(); if (n == 0) { cout << endl; return ; } rep(i,n) vmint(v[i]); } #include random_device rd; mt19937_64 mt(rd()); void shf(vector &a){ int n = a.size(); rep(i,n){ int j = i + (mt() % (n - i)); swap(a[i],a[j]); } } void solve(){ int n; cin >> n; ll m; cin >> m; map mp; rep(i,n){ ll x; cin >> x; mp[x%m]++; } int ans = 0; set st; for (auto p : mp){ ll x = p.first; int cnt = p.second; if (st.find(x) != st.end()) continue; if ((x + x) % m == 0){ ans++; continue; } ans += max(cnt,mp[m-x]); st.insert(x), st.insert(m-x); } o(ans); } int main(){ fast_io(); int t = 1; //cin >> t; while (t--) solve(); }