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       # MATH introduce subtraction
[hear] (intro -);

[hear] (= (unary 1 1 1 0) / - (unary 1 1 1 1 0) (unary 1 0));

[hear] (= (unary 1 1 1 0) / - (unary 1 1 1 1 1 1 1 0) (unary 1 1 1 1 0));

[hear] (= (unary 0) / - (unary 1 0) (unary 1 0));

[hear] (= (unary 1 1 0) / - (unary 1 1 1 1 1 0) (unary 1 1 1 0));

[hear] (= (unary 0) / - (unary 1 1 0) (unary 1 1 0));

[hear] (= (unary 1 0) / - (unary 1 0) (unary 0));

[hear] (= (unary 1 1 1 1 0) / - (unary 1 1 1 1 1 1 1 1 0) (unary 1 1 1 1 0));

[hear] (= (unary 1 1 1 0) / - (unary 1 1 1 1 0) (unary 1 0));

[hear] (= (unary 1 1 1 1 0) / - (unary 1 1 1 1 1 1 1 1 0) (unary 1 1 1 1 0));

[hear] (= (unary 1 0) / - (unary 1 0) (unary 0));