set s [gets stdin]
set g [split $s .]
set flag 0
foreach { ss } $g {
    if {![regexp {^[0-9a-z]+$} $ss]} {
        set flag 1
    }
}
if { [string length [lindex $g end] ] < 2 || [string length [lindex $g end] ] > 3 } {
    set flag 1
}
if { $flag == 0 } {
    puts YES
} else  {
    puts NO
}