import java.io.IOException;
import java.io.InputStream;
import java.util.NoSuchElementException;

public class New {
    private static final Value used=new Value(-1,-1);
    public static void main(String[] args) {
        FastScanner scanner=new FastScanner();
        int len=scanner.readInt().intValue;
        Value[] unsorted=new Value[len];
        Value[] sorted=new Value[len];
        String[] toStringedNumbers=new String[len];
        int sum=0;
        for(int i=0;i<len;i++){
            readInt r=scanner.readInt();
            int readI=r.intValue;
            Value value=new Value(readI,i);
            unsorted[i]=value;
            sorted[readI-1]=value;
            toStringedNumbers[readI-1]=r.value;
            sum+=r.value.length();
        }
        sorted[unsorted[len-1].value-1]=used;

        int[] result=new int[len];
        int offset=0;
        for(int i=0,filled=0;filled<len;filled+=2,i++){
            i=findMin(sorted,i);
            Value value=sorted[i];
            int next=findNext(unsorted,value.offset);
            result[offset++]=value.value;
            result[offset++]=unsorted[next].value;

            remove(sorted,unsorted,value);
            remove(sorted,unsorted,unsorted[next]);
        }
        StringBuilder sb=new StringBuilder(sum+len);
        for(int i=0;i<len;i++){
            sb.append(toStringedNumbers[result[i]-1]);
            if(i!=len-1)sb.append(" ");
        }
        System.out.println(sb);
    }
    private static int findMin(Value[] sortedArr,int start){
        for(int i=start;i<sortedArr.length;i++){
            if(sortedArr[i]!=used) return i;
        }
        throw new RuntimeException();
    }
    private static int findNext(Value[] unsorted,int start){
        for(int i=start+1;i<unsorted.length;i++){
            if(unsorted[i]!=used) return i;
        }
        throw new RuntimeException();
    }
    private static void remove(Value[] sorted,Value[] unsorted,Value v){
        sorted[v.value-1]=used;
        unsorted[v.offset]=used;
    }
    private record readInt(int intValue,String value){}

    private record Value(int value,int offset){}
    private static class FastScanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;
        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            }else{
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return buflen > 0;
            }
        }
        private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
        private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}

        public readInt readInt(){
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            int n=0;
            while(true){
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                }else if(b == -1 || !isPrintableChar(b)){
                    return new readInt(n,sb.toString());
                }else{
                    throw new NumberFormatException();
                }
                sb.append((char)b);
                b = readByte();
            }
        }
    }
}