U11 tt N activate N U21 tt M N s plus activate N activate M and tt X activate X isNat n__0 tt isNat n__plus V1 V2 and isNat activate V1 n__isNat activate V2 isNat n__s V1 isNat activate V1 plus N 0 U11 isNat N N plus N s M U21 and isNat M n__isNat N M N 0 n__0 plus X1 X2 n__plus X1 X2 isNat X n__isNat X s X n__s X activate n__0 0 activate n__plus X1 X2 plus X1 X2 activate n__isNat X isNat X activate n__s X s X activate X X 2.2 U21 tt M N plus activate N activate M isNat n__s V1 activate V1 isNat n__plus V1 V2 activate V1 plus N 0 U11 isNat N N isNat n__plus V1 V2 and isNat activate V1 n__isNat activate V2 isNat n__plus V1 V2 isNat activate V1 isNat n__plus V1 V2 activate V2 plus N s M isNat M activate n__0 0 plus N 0 isNat N isNat n__s V1 isNat activate V1 U11 tt N activate N plus N s M and isNat M n__isNat N activate n__isNat X isNat X and tt X activate X U21 tt M N activate N U21 tt M N s plus activate N activate M activate n__plus X1 X2 plus X1 X2 activate n__s X s X U21 tt M N activate M plus N s M U21 and isNat M n__isNat N M N true plus N s M U21 and isNat M n__isNat N M N U21 tt M N activate M isNat n__plus V1 V2 activate V2 isNat n__plus V1 V2 isNat activate V1 activate n__plus X1 X2 plus X1 X2 U21 tt M N activate N and tt X activate X activate n__isNat X isNat X isNat n__plus V1 V2 and isNat activate V1 n__isNat activate V2 plus N 0 U11 isNat N N isNat n__plus V1 V2 activate V1 plus N s M and isNat M n__isNat N U11 tt N activate N isNat n__s V1 activate V1 isNat n__s V1 isNat activate V1 plus N 0 isNat N U21 tt M N plus activate N activate M plus N s M isNat M true 0 0 0 U21 3 2 3 25911 U11 2 2 0 s 1 1 25908 isNat 1 1 0 activate 1 1 0 and 2 1 2 0 plus 2 1 2 2 activate 1 1 0 n__s 1 1 25908 0 0 47339 s 1 0 n__isNat 1 1 1 n__plus 2 1 2 3 n__0 0 47339 isNat 1 1 1 plus 2 1 2 3 U11 2 2 1 U21 3 2 3 3 tt 0 2241 and 2 2 1 isNat n__0 tt activate n__isNat X isNat X plus N s M U21 and isNat M n__isNat N M N U11 tt N activate N and tt X activate X activate n__s X s X activate X X isNat n__plus V1 V2 and isNat activate V1 n__isNat activate V2 plus X1 X2 n__plus X1 X2 plus N 0 U11 isNat N N activate n__plus X1 X2 plus X1 X2 s X n__s X isNat X n__isNat X 0 n__0 activate n__0 0 isNat n__s V1 isNat activate V1 U21 tt M N s plus activate N activate M U21 tt M N s plus activate N activate M false activate n__0 0 false activate n__s X s X false NaTT certifiable-1.6