#!/usr/bin/env tclsh9.0

set lefts [list]
set rights [list]

foreach line [split [read stdin] \n] {
    if {$line eq ""} continue
    lassign $line l r
    lappend lefts $l
    lappend rights $r
}

foreach r $rights {
    incr count($r)
}

set total 0
foreach l $lefts {
    if {[info exists count($l)]} {set c $count($l)} else {set c 0}
    incr total [expr {$l * $c}]
}
puts $total