Let
**
$f(x) = \sqrt{1^{2} + 2^{2} + 3^{2} + \cdots + (x-1)^{2} + x^{2}}$
**
.

Find the minimum value of
$n \geq2$
such that
**
$f(n)$
**
is a positive integer.

$n$ is a positive integer.

**
Clarification
**
:
$f(x)$
denote the square root of the sum of the squares of first
$x$
positive integers.

The answer is 24.

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