s
u
m
m
a
t
i
o
n
s
t
e
p
s
1
1
π
≈
1
2
1
∑
k
=
0
k
(
-
1
)
(
6
k
)
!
(
1
3
5
9
1
4
0
9
+
5
4
5
1
4
0
1
3
4
k
)
(
3
k
)
!
3
(
k
!
)
3
k
+
3
2
6
4
0
3
2
0
n
u
m
b
e
r
o
f
d
i
g
i
t
s
m
a
t
c
h
e
d
:
2
7
π
≈
3
.
1
4
1
5
9
2
6
5
3
5
8
9
7
9
3
2
3
8
4
6
2
6
4
3
3
8
