typo: Double word "of"

spec/expressions.md

@@ -2481,7 +2481,7 @@ For an operation of the form `-x`, unary operator overload resolution ([Unary op
    long operator -(long x);
    ```
 
-   The result is computed by subtracting `x` from zero. If the value of of `x` is the smallest representable value of the operand type (-2^31 for `int` or -2^63 for `long`), then the mathematical negation of `x` is not representable within the operand type. If this occurs within a `checked` context, a `System.OverflowException` is thrown; if it occurs within an `unchecked` context, the result is the value of the operand and the overflow is not reported.
+   The result is computed by subtracting `x` from zero. If the value of `x` is the smallest representable value of the operand type (-2^31 for `int` or -2^63 for `long`), then the mathematical negation of `x` is not representable within the operand type. If this occurs within a `checked` context, a `System.OverflowException` is thrown; if it occurs within an `unchecked` context, the result is the value of the operand and the overflow is not reported.
 
    If the operand of the negation operator is of type `uint`, it is converted to type `long`, and the type of the result is `long`. An exception is the rule that permits the `int` value -2147483648 (-2^31) to be written as a decimal integer literal ([Integer literals](lexical-structure.md#integer-literals)).