problem number 04, This is good co_primen.txt

problem number: 04, This is good co-primen
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QUESTION:-
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Co-primes, while not being the most exciting thing in the world, are extremely useful for cryptography (among other things). Numbers are co-prime if they don't share any common factors above 1.

For example, 15 and 8 are not prime, but have factors of 3 5 and 2 4 respectively, and so are co-prime. 15 and 9 are not co-prime, since they share a factor of 3.

For your input number, what is the sum of the positive co-primes of that number which are less than that number?

For example, the coprimes of 15 are
1 2 4 7 8 11 13 14


If your input was 15, the answer would be 60.

GIVEN INPUT:-
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987820

ANSWER:-
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q)
q)
q)
q)
q)co_prime:{a:(where 0=x mod (til x))except 1; l:til x; i:0; while[i<count a; c,:where 0= l mod (a i); i+:1]; v:l except (distinct c); sum v}
q)
q)
q)co_prime[987820]
195153719200
q)
q)
q)