begin process p1
begin mutex
print aaaa
print bbbb
print cccc
print dddd
print eeee
print ffff
end mutex
print gggg
end process
begin process p2
recv p4 ****
print xxxx
print yyyy
end process
begin process p3
print 1111
print 2222
print 3333
end process
begin process p4
print &&&&
print $$$$
send p2 ****
print ^^^^
end process