function Stacker(){

var stack = [];

this.size = function() {

return stack.length;

}

this.push = function() {

for(var i =0; i < arguments.length; i+= 1) {

stack.push(arguments[i]);

}

}

this.pop = function(){

if (stack.length > 0 ) {

return stack.pop();

} else {

return null;

}

}

}

function altPop(o) {

var j = o.size()

, i = 0

, output = []

, p;

while (i < j ) {

p = o.pop();

if (i % 2 === 0) {

output.push( p );

}

i += 1;

}

return output.join(' ');

}

var fs = require("fs")

, nums

, j = 0

, i = 0

, _obj

;

fs.readFileSync(process.argv[2]).toString().split('\n').forEach(function (line) {

if (line !== "") { // ignore empty lines

nums = line.split(' ');

i = 0

j = nums.length;

_obj = new Stacker();

while (i < j) {

_obj.push(nums[i]);

i += 1;

}

console.log( altPop(_obj) );

}

});