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Balkan MO Shortlist
2009 Balkan MO Shortlist
A1
Find all possible values of
Find all possible values of
Source: Balkan MO ShortList 2009 A1
April 6, 2020
Problem Statement
Let
N
∈
N
N \in \mathbb{N}
N
∈
N
and
x
k
∈
[
−
1
,
1
]
x_k \in [-1,1]
x
k
∈
[
−
1
,
1
]
,
1
≤
k
≤
N
1 \le k \le N
1
≤
k
≤
N
such that
∑
k
=
1
N
x
k
=
s
\sum_{k=1}^N x_k =s
∑
k
=
1
N
x
k
=
s
. Find all possible values of
∑
k
=
1
N
∣
x
k
∣
\sum_{k=1}^N |x_k|
∑
k
=
1
N
∣
x
k
∣
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