#!/usr/bin/perl
use strict;
my $debug= 0;
my $lisp= "";
#
# S -> ( Op Opd* )
# Op -> + | * | - | /
# Opd -> S | Number
#
my @tokens;
my $pos= 0;

sub lisp {
        print "lisp_eval [$pos] token [$tokens[$pos]]\n"
               
 if $debug;
        # throw away (
        $pos ++;
        
        my $op= $tokens[$pos++];
        my @operands= ();
        while( $pos < scalar( @tokens ) ) {
               
 last if( $tokens[$pos] eq ")" );
               
 push @operands, operand();
        }

        return [$op, @operands];
}
sub operand {
        print "operand_eval [$pos] token [$tokens[$pos]]\n"
               
 if $debug;
        my $next= $tokens[$pos];
        if( $next =~ m/\d+/ ) {
               
 $pos ++;
               
 return $next;
        } else {
               
 return lisp();
        }
}

sub rewrite_perl {
        my @root= @{ shift() };
        my $op= $root[0];
        my @opds= ();
        foreach( 1 .. @root - 1 ) {
               
 if( ref $root[$_] eq "ARRAY" ) {
               
         push @opds, rewrite_perl( $root[$_] );
               
 } else {
               
         push @opds, $root[$_];
               
 }
        }
        my $code= $opds[0];
        foreach( 1 .. @opds - 1 ) {
               
 $code= "( $code $op $opds[$_] )";
        }
        return $code;
}
sub myread { $pos= 0; my $line= <STDIN>; @tokens= split /\s+/, $line; }

LOOP: print eval ( rewrite_perl lisp( myread ) ), $/; goto LOOP;