NOT returns the bitwise Boolean inverse of I. 
Fortran 90 and later, has overloads that are GNU extensions
Elemental function
RESULT = NOT(I) 
| I | The type shall be INTEGER. | 
The return type is INTEGER, of the same kind as the argument. 
| Name | Argument | Return type | Standard | 
| NOT(A) | INTEGER A | INTEGER | Fortran 95 and later | 
| BNOT(A) | INTEGER(1) A | INTEGER(1) | GNU extension | 
| INOT(A) | INTEGER(2) A | INTEGER(2) | GNU extension | 
| JNOT(A) | INTEGER(4) A | INTEGER(4) | GNU extension | 
| KNOT(A) | INTEGER(8) A | INTEGER(8) | GNU extension | 
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    https://gcc.gnu.org/onlinedocs/gcc-10.2.0/gfortran/NOT.html