1
STRUCTURES
2
ARTIFICIAL
3
RESISTANT
4
NATURAL
5
STABLE
X
M
Z
X
S
E
E
L
E
L
O
A
M
Y
A
J
T
O
L
I
P
D
N
I
S
O
R
C
A
I
A
V
A
A
W
U
E
A
T
J
B
O
R
O
T
A
Y
V
R
C
I
Z
L
C
U
O
X
H
G
A
U
B
F
O
E
I
T
H
V
O
T
C
T
G
I
T
T
S
A
P
R
I
K
N
C
A
C
C
L
E
N
I
K
I
I
E
U
O
I
P
N
K
I
V
U
X
U
R
R
I
A
I
Q
U
U
E
U
A
A
A
T
I
L
Q
X
O
O
I
V
Y
O
V
S
U
R
E
S
I
S
T
A
N
T
Y