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