function triangle(s) {
  var chars = {'R':0,'G':2,'B':3};
  var ch = "R GB"
  var tab = [0,1,3,2,2,0,3,1,1,3]
  y = []
  //s = s.split('').map(x=>chars[x])
  rl = s.length-1
  for(**0;i<=rl;i++)
    y.push(chars[s[i]])

  for(j=rl;j>0;j--)
    for(**0; i<j;i++){
      //  x = (y[i])^(y[i+1])
       y[i] =  tab[(y[i])+(y[i+1])]
      }
  return ch[y[0]]
}