/**
 * @param {string[][]} message
 * @return {string}
 */
function decode(message) {
  // your code here
  let r=0
  let c=0
  let ans = ""
  let direction = 1
  for(c=0; c<message[0].length; c++){
    ans += message[r][c]

    if(direction>0){
      if(r === message.length -1){
        direction = - direction
      }
    }else{
      if(r === 0){
        direction = 1
      }
    }
    r += direction
  }
  return ans 
}