Logical operator outside parentheses

I can't figure out what the logical operator "not" (~/!), does in front of a parenthesis.

Here is the task:

I have a = 1, b = 2 and c = 2.

and this if statement:

if (a ~= b | a ~= c) &&~(a ~= b && a ~= c && b ~= c)

What does it mean having a logical operator "not" before the parenthesis (look at the bold ~)?