v -25 0 -25
v 25 0 -25
v 25 0 25
v -25 0 25
v 0 50 0 
c 0 0 0
l 0 1
l 0 3
l 0 4
l 1 2
l 1 4
l 2 3
l 2 4
l 3 4
#first number indicate how may lines in the face
#line index starting from 1.  If it is negative, it means reverse the staring
# and ending point of line
f 3 -1 3 -5
f 3 5 -7 -4
f 3 7 -8 -6
f 3 8 -3 2
f 4 1 4 6 -2