Ton

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_ check_assoc(op, a, b, c) {
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  return op(op(a, b), c) == op(a, op(b, c));
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}
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int main(int x, int y, int z) {
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  return check_assoc(_+_, x, y, z);
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}
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{-
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    method_id | in         | out
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TESTCASE | 0  | 2 3 9      | -1
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TESTCASE | 0  | 11 22 44   | -1
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TESTCASE | 0  | -1 -10 -20 | -1
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-}
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