gistfile1.rb

st = gets.chomp
w = st.dup
correct = true
l = st.length
i=0
while i<l
    if w[i..i]=='z'
        w[i..i]='T'
    else
        if (w[i..i] != 'a')and(w[i..i] !='b')
            correct=false
        end
    end
    i=i+1
end
if not correct
    puts 'Izn\'t correct simbols'
else
   w_old=w.dup
   while w.length>1
        w=w.gsub('aT','T')
        w=w.gsub('bTT','T')
        if(w==w_old)
            w='N'
        end
        w_old=w.dup
   end
    if w=='T'
        puts st+' - corret word'
    else
        puts st+' - uncorrect word'
    end   
end