set line [gets stdin]
scan $line "%s" s
if [regexp {^[a-z0-9]+[a-z0-9\.]*\.+[a-z0-9]{2,3}$} $s matchresult] {
    if [regexp {\.\.} $s matchresult] {
        puts "NO"
    } else {
        puts "YES"
    }
} else {
    if [regexp {^[a-z0-9]{2,3}$} $s match] {
        puts "YES"
    } else {
        puts "NO"
    }
}