For Loop Sum – 1 | Exact Science

For Loop Sum – 1

Problem Statement

Given a number n, compute the sum:

1 + 1/2² + 1/3² + … + 1/n²

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Input

A single integer n (1 ≤ n ≤ 100000).

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Output

Print the value of the sum.

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Example

input	output
2	1.25

Factorial (for loop)

Binomial Coefficient

Geometric Progression

For Loop Sum – 1

For Loop Sum – 2