parseInt(x) = parse(Int, x)
parseMap(x::Array{SubString{String},1}) = map(parseInt, x)

function main()
    s = readline() |> chomp
    l = length(s)
    f = 0
    for i in 1:l
        if i%2==1&&(Int(s[i])<97||Int(s[i])>122)
            f = 1
        end
        if i%2==0&&s[i]!=' '
            f = 1
        end
    end
    println(f==0 ? "Yes" : "No")
end
main()