#include <bits/stdc++.h>

using namespace std;

#define REP(i, N) for (int i = 0; i < (int)N; i++)
#define FOR(i, a, b) for (int i = a; i < (int)b; i++)
#define ALL(x) (x).begin(), (x).end()
#define INF (1 << 30)
#define LLINF (1LL << 62)
#define DEBUG(...) debug(__LINE__, ":" __VA_ARGS__)

constexpr int MOD = 1000000007;
using ll = long long;
using Pii = pair<int, int>;
using Pll = pair<ll, ll>;

template <class T>
string to_string(T s);
template <class S, class T>
string to_string(pair<S, T> p);
string to_string(string s);
string to_string(const char s[]) { return string(s); }

template <class T>
string to_string(T v) {
  if (v.empty()) return "{}";
  string ret = "{";
  auto itr = v.begin(), next = ++v.begin();
  for (; next != v.end(); ++itr, ++next) ret += to_string(*itr) + ",";
  ret += to_string(*itr) + "}";
  return ret;
}
template <class S, class T>
string to_string(pair<S, T> p) {
  return "{" + to_string(p.first) + "," + to_string(p.second) + "}";
}
string to_string(string s) { return s; }

void debug() { cerr << endl; }
template <class Head, class... Tail>
void debug(Head head, Tail... tail) {
  cerr << to_string(head) << " ";
  debug(tail...);
}
void print() { cout << endl; }
template <class Head, class... Tail>
void print(Head head, Tail... tail) {
  cout << to_string(head) << " ";
  print(tail...);
}

struct IO {
#ifdef _WIN32
  inline char getchar_unlocked() { return getchar(); }
  inline void putchar_unlocked(char c) { putchar(c); }
#endif
  string separator = " ";
  template <class T>
  inline void read(T &x) {
    char c;
    do {
      c = getchar_unlocked();
    } while (c != '-' && (c < '0' || '9' < c));
    bool minus = 0;
    if (c == '-') {
      minus = 1;
      c = getchar_unlocked();
    }
    x = 0;
    while ('0' <= c && c <= '9') {
      x *= 10;
      x += c - '0';
      c = getchar_unlocked();
    }
    if (minus) x = -x;
  }
  inline void read(string &x) {
    char c;
    do {
      c = getchar_unlocked();
    } while (c == ' ' || c == '\n');
    x.clear();
    do {
      x += c;
      c = getchar_unlocked();
    } while (c != ' ' && c != '\n' && c != EOF);
  }
  template <class T>
  inline void read(vector<T> &v) {
    for (auto &x : v) read(x);
  }
  template <class Head, class... Tail>
  inline void read(Head &head, Tail &... tail) {
    read(head);
    read(tail...);
  }
  template <class T>
  inline void write(T x) {
    char buf[32];
    int p = 0;
    if (x < 0) {
      x = -x;
      putchar_unlocked('-');
    }
    if (x == 0) putchar_unlocked('0');
    while (x > 0) {
      buf[p++] = (x % 10) + '0';
      x /= 10;
    }
    while (p) {
      putchar_unlocked(buf[--p]);
    }
  }
  inline void write(string x) {
    for (char c : x) putchar_unlocked(c);
  }
  inline void write(const char s[]) {
    for (int i = 0; s[i] != 0; ++i) putchar_unlocked(s[i]);
  }
  template <class T>
  inline void write(vector<T> v) {
    for (auto itr = v.begin(); itr + 1 != v.end(); ++itr) {
      write(*itr);
      write(separator);
    }
    write(v.back());
  }
  template <class Head, class... Tail>
  inline void write(Head head, Tail... tail) {
    write(head);
    write(separator);
    write(tail...);
  }
  void set_separator(string s) { separator = s; }
} io;

int main() {
  int N;
  io.read(N);
  vector<int> A(N);
  io.read(A);
  sort(ALL(A), greater<int>());
  map<int, int> mp;
  for (auto x : A) mp[x]++;
  int ans = 0;
  REP(i, N) {
    if (mp[A[i]] < 1) continue;
    REP(t, 31) {
      int x = 1 << t;
      int pad = x - A[i];
      if (mp.count(pad) && (mp[pad] > (A[i] == pad))) {
        ans++;
        mp[pad]--;
        mp[A[i]]--;
        break;
      }
    }
  }
  io.write(ans);
  io.write("\n");
  return 0;
}
#include <bits/stdc++.h>
 
using namespace std;
inline void prep ()
{
  cin.tie (0);
  cin.sync_with_stdio (0);
};
const double pi = acos(-1.);
//printf(%.12lf\n,mid);
// __builtin_popcount(int) count 1's in binary
// get decimal part of number
/*
double intpart;
double thiss = modf((double)(n*m)/(double)k, &intpart);
*/
// round = (int)(num+.5)
long long mod = 1000000007;
 
long long mymod(long long num){
  if (num< 0 && !(num%mod == 0)){
    if (mod == 1){
      return 0;
    }
    return mod-abs(num)%mod;
  }else{
    return num%mod;
  }
}
 
/*string sentence = And I feel fine...;
    istringstream iss(sentence);
*/  
 
double eps = .000000001;

int main(){
  prep();
  int n, m;
  cin >> n >> m;
  int arr[n][m];
  for (int i=0; i<n; i++){
      for (int j=0; j<m; j++){
          cin >> arr[i][j];
          arr[i][j]--;
      }
  }
  int pointers[n] = {0};
  int cnts[m] = {0};
  int res = 0;

  for (int i=0; i<n; i++){
      cnts[arr[i][0]]++;
  }
  for (int i=0; i<m; i++){
      res = max(res, cnts[i]);
  }
  bool erased[m] = {false};
  for (int x=0; x<m-1; x++){
      int maxx = 0;
      int maxind = 0;
      for (int i=0; i<m; i++){
          if (cnts[i] > maxx){
              maxx = cnts[i];
              maxind = i;
          }
      }
      erased[maxind] = true;
      for (int i=0; i<n; i++){
          cnts[arr[i][pointers[i]]]--;
          while (erased[arr[i][pointers[i]]]){
              pointers[i]++;
          }
          cnts[arr[i][pointers[i]]]++;
          
      }
      maxx = 0;
      for (int i=0; i<m; i++){
          maxx = max(cnts[i], maxx);
      }
      res = min(res, maxx);
  }
  cout << res;
  return 0; 
}