C :

#include <stdio.h>
#include <stdlib.h>
int main()
{
	int i,j,n,t,a[1001]={0};
    n=20;
    for (i=1;i<=n;i++)
		scanf("%d",&a[i]);
    for (i=1;i<=n-1;i++)
     for (j=i+1;j<=n;j++)
     {
		if (a[i]>a[j])
        {
			t=a[i]; a[i]=a[j]; a[j]=t;
        }
     } 
    printf("%d",a[1]); 
    for (i=3;i<=n;i=i+2)
		printf(" %d",a[i]);
    printf("\n");
	return 0;
}

C++ :

#include<iostream>
using namespace std;
int main()
{
	int n,z;
	int f[20];
	for(int i=1;i<=20;i++)
	{cin>>n;
	f[i]=n;
	}
	for(int q=1;q<=20;q++)
	for(int x=2;x<=20;x++)
	{
		if(f[x-1]>f[x]) {
		z=f[x];f[x]=f[x-1];f[x-1]=z;}
	};
	for(int p=1;p<=19;p+=2)
	{if(p!=19) cout<<f[p]<<" ";
	else cout<<f[p];
	}
	cout<<endl;
	return 0;
}

Pascal :

var a:array[1..100]of integer;i,j:integer;
begin
 for i:=1 to 20 do
  read(a[i]);
 readln;
 for i:=1 to 19 do
  for j:=1 to 20-i do
   if a[j]>a[j+1]then begin a[j]:=a[j]xor a[j+1];a[j+1]:=a[j]xor a[j+1];a[j]:=a[j]xor a[j+1] end;
 for i:=1 to 9 do
  write(a[2*i-1],' ');
 writeln(a[19])
end.