Programming olympiad

There are $n$ participants arrived to ACM competition. As a result of the survey, the jury found that $a$ participants code in C, $b$ in Python, $c$ in Pascal, $x$ simultaneously know C and Python, $y$ - Python and Pascal, $z$ - C and Pascal. Given the values $n$, $a$, $b$, $c$, $x$, $y$, $z$, find the number of participants who program in three programming languages.