# Aromatic plants

0.55 A friend of Professor Oak suggested him including some aromatic
plants in his garden, and Prof. Oak thought that it was such a good
idea. As you can see, now he has 11 such plants: 5 in the top row, and 6
in the bottom row. Hmm\... so we have a prime number and a composite
number that add up to a prime number. How common is that?

0.40 ![image](aromatiques.eps){width="5.9cm"}

## Input

Input consists of several cases, each with an integer $n$ between 2 and
$10^7$.

## Output

For every $n$, print the number of triples of integer numbers
$(a, b, c)$ such that:

- the three numbers are between 2 and $n$,

- $a$ is prime, $b$ is composite, $c$ is prime,

- and $a + b = c$.

## Problem information

Author: Salvador Roura\
Event: Vint-i-quatrè Concurs de Programació de la UPC - Semifinal\
Date: 2026-06-18

Generation: 2026-06-10T18:32:17.892Z

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