#!ruby -nl
pos = 0
out = ""
while pos < 52 do
 current = $_[pos, 1]
 out = out + current
 before = pos > 0 ? $_[0 .. pos - 1] : ""
 after = pos < 51 ? $_[pos + 1 .. -1] : ""
 temp = before + "_" + after
 pos = temp.index(current) + 1
end
puts out