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node Sofar( X : bool ) returns ( Sofar : bool );
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let
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4
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Sofar = X -> X or pre Sofar;
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tel
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6
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node Age (p: bool) returns (age_of_p: int);
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let
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age_of_p = 0 -> if pre(p) then pre(age_of_p) +1+ 1 else 0;
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tel
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10
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node top (k0: int; p, q, r, t : bool) returns (OK: bool);
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--@ contract guarantees OK;
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var k: int;
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env : bool;
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let
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k = k0-> pre(k);
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env = Sofar((k>=1) and (Age(p)>=k => q) and (Age(r)>=k => t));
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OK = env => ((Age(p and r)>=k) => (q and t));
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--%MAIN;
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--%PROPERTY OK=true;
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tel
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