#include <bits/stdc++.h>
using namespace std;
#define int              long long int
#define double           long double
#define print(a)         for(auto x : a) cout << x << " "; cout << endl
inline int power(int a, int b) {
    int x = 1;
    while (b) {
        if (b & 1) x *= a;
        a *= a;
        b >>= 1;
    }
    return x;
}


const int M = 1000000007;
const int N = 3e5+9;
const int INF = 2e9+1;
const int LINF = 2000000000000000001;

//_ ***************************** START Below *******************************

vector<int> a;
vector<int> generateOrder(int n, int valleys){
	int s = 0, e = n-1;
	vector<int> order(n);
	
	int j = 0;
	for(int i=1; i<n; i+=2){
		order[i] = a[j];
		j++;
	}
	for(int i=0; i<n; i+=2){
		order[i] = a[j];
		j++;
	}
	
	return order;
}

bool isPossible(int n, int mid){
	vector<int> valleys(n);
	
	int j = 0;
	for(int i=1; i<n; i+=2){
		valleys[i] = a[j];
		j++;
	}
	for(int i=0; i<n; i+=2){
		valleys[i] = a[j];
		j++;
	}
	
	int ct = 0;
	for(int i=1; i<n-1; i+=2){
		if(valleys[i] < valleys[i-1] && valleys[i] < valleys[i+1]) ct++;
	}

	return ct >= mid;
}

pair<int, vector<int>> consistency1(int n){
	
	sort(begin(a), end(a));

	int s = 0, e = n;
	while(s<e){
		int mid = s + (e-s+1)/2;
		if(isPossible(n, mid)){
			s = mid;
		}
		else e = mid-1;
	}
	
	return {e, generateOrder(n, e) };

}






pair<int, vector<int>> consistency2(int n){
	
	sort(begin(a), end(a));
	vector<int> order(n);
	
	int j = 0;
	for(int i=1; i<n; i+=2){
		order[i] = a[j];
		j++;
	}
	for(int i=0; i<n; i+=2){
		order[i] = a[j];
		j++;
	}
	
	int ct = 0;
	for(int i=1; i<n-1; i+=2){
		if(order[i] < order[i-1] && order[i] < order[i+1]) ct++;
	}

	
	return {ct, order };

}










void solve() {
    
    int n;
    cin>>n;
    
    a.resize(n);
    for(int i=0; i<n; i++) cin >> a[i];
    
    auto ans1 = consistency1(n);
    
    cout << ans1.first << endl;
    for(auto& it : ans1.second){
        cout << it << " ";
    }cout << endl;
    
    
    
    // cout << " : " << endl;
    
    
    // auto ans2 = consistency2(n);
    
    // cout << ans2.first << endl;
    // for(auto& it : ans2.second){
    //     cout << it << " ";
    // }cout << endl;


}





int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}