/in/foo.c: In function 'main':
/in/foo.c:5:18: warning: unused variable 'i' [-Wunused-variable]
  int a,b,c,delta,i;
                  ^
/in/foo.c:14:8: warning: 'z' may be used uninitialized in this function [-Wmaybe-uninitialized]
  else {printf("%.2lf",z);}
        ^~~~~~~~~~~~~~~~~