/in/foo.c: In function 'main':
/in/foo.c:11:40: warning: 'i' may be used uninitialized in this function [-Wmaybe-uninitialized]
    else if(delta<0) {x=(-b+sqrt(-delta)*i)/2*a,y=(-b-sqrt(-delta)*i)/2*a;
                            ~~~~~~~~~~~~^~