what is the concept of evaluation of expression z = (y = 30) + (y = 10) + (y = 20);

strong text`What is the output of the following code please help...i'm not getting any compiler error

how the compiler evaluates such expression

    #include <stdio.h>
    int main()
    {
        int y = 3;

        **int z =  (y = 30) + (y = 10) + (y = 20);**
        `print z`
        printf("%d\n", z);
        `print y`
        printf("%d\n",y);
    }