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-module(problem45).
-export([solve/1]).
triangles(M) -> [ (N * (N + 1)) div 2 || N <- lists:seq(1,M) ].
pentagons(M) -> [ (N * ((3 * N) - 1)) div 2 || N <- lists:seq(1,M) ].
hexagons(M) -> [ N * ((2 * N) + 1) || N <- lists:seq(1,M) ].
max(M) -> M * ((2 * M) + 1).
nums(M) ->
T = triangles(M),
P = pentagons(M),
H = hexagons(M),
[ X || X <- lists:seq(1,max(M)), lists:member(X,T), lists:member(X, P), lists:member(X,H) ].
getnext([_]) -> "Keep trying.";
getnext([40755,X|_]) -> X;
getnext([_|T]) -> getnext(T).
solve(M) -> getnext(nums(M)).
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