f
i
r
s
t
t
e
r
m
a
1
l
a
s
t
t
e
r
m
z
1
0
0
n
u
m
b
e
r
o
f
t
e
r
m
s
n
1
0
0
1
+
2
+
3
+
…
+
1
0
0
+
1
0
0
+
9
9
+
9
8
+
…
+
1
=
1
0
1
+
1
0
1
+
1
0
1
+
…
+
1
0
1
T
h
e
r
e
f
o
r
e
1
+
2
+
3
+
…
+
1
0
0
=
1
0
1
×
1
0
0
2
=
5
0
5
0