#include <bits/stdc++.h>
constexpr auto Inf = 0X3F3F3F3F;
using namespace std;
namespace IO {
inline long long read() {
  long long o = 0, f = 1;
  char c = getchar();
  while (c < '0' || c > '9') {
    if (c == '-') f = -1;
    c = getchar();
  }
  while (c > '/' && c < ':') {
    o = o * 10 + c - '0';
    c = getchar();
  }
  return o * f;
}
inline char recd() {
  char o;
  while ((o = getchar()) < '0' || o > '9')
    ;
  return o;
}
inline double reod() {
  double o = read(), f = 1;
  char c;
  while ((c = getchar()) > '/' && c < ':') o += (c - '0') / (f *= 10);
  return o;
}
}  // namespace IO
using namespace IO;
const int SIZE = 2E5 + 7, Mod = 1E9 + 7;
int a[SIZE], b[SIZE], c[SIZE];
int main() {
  int N = read();
  for (int pos = 1; pos <= N; pos++) a[pos] = read();
  sort(a + 1, a + 1 + N);
  int L = 1, R = N;
  for (int pos = 1; pos <= N; pos += 2) b[pos] = a[L++];
  for (int pos = 2; pos <= N; pos += 2) b[pos] = a[R--];
  L = 1, R = N;
  for (int pos = 2; pos <= N; pos += 2) c[pos] = a[L++];
  for (int pos = 1; pos <= N; pos += 2) c[pos] = a[R--];
  int r1 = 0, r2 = 0;
  for (int pos = 2; pos < N; pos++)
    if (b[pos] < b[pos - 1] && b[pos] < b[pos + 1]) r1++;
  for (int pos = 2; pos < N; pos++)
    if (c[pos] < c[pos - 1] && c[pos] < c[pos + 1]) r2++;
  if (r1 > r2) {
    printf("%d\n", r1);
    for (int pos = 1; pos <= N; pos++) printf("%d ", b[pos]);
  } else {
    printf("%d\n", r2);
    for (int pos = 1; pos <= N; pos++) printf("%d ", c[pos]);
  }
}
