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Switzerland Team Selection Test
2003 Switzerland Team Selection Test
9
9
Part of
2003 Switzerland Team Selection Test
Problems
(1)
5050 | a_k +a_l -a_m -a_n when 0 < a_1 < a_2 <... < a_{101} < 5050
Source: Switzerland - Swiss TST 2003 p9
2/18/2020
Given integers
0
<
a
1
<
a
2
<
.
.
.
<
a
101
<
5050
0 < a_1 < a_2 <... < a_{101} < 5050
0
<
a
1
<
a
2
<
...
<
a
101
<
5050
, prove that one can always choose for different numbers
a
k
,
a
l
,
a
m
,
a
n
a_k,a_l,a_m,a_n
a
k
,
a
l
,
a
m
,
a
n
such that
5050
∣
a
k
+
a
l
−
a
m
−
a
n
5050 | a_k +a_l -a_m -a_n
5050∣
a
k
+
a
l
−
a
m
−
a
n
number theory
combinatorics
divides