Let
be positive integers such that
Show that at least two of the numbers are even.
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Let $ n_1, n_2, \ldots, n_{1998} $ be positive integers such that $ n_1^2 + n_2^2 + \cdots + n_{1997}^2 = n_{1998}^2. $ Show that at least two of the numbers are even.
Školjka