请求大佬帮改

#include <stdio.h>
double a,b,c,d;
double fc(double x){
    return a*x*x*x+b*x*x+c*x+d;
}
int main(){
    scanf("%lf%lf%lf%lf",&a,&b,&c,&d);
    double left,right,x1,x2;
    double mid;
    int cnt=0;
    for(left=-100,right=-99;right<=100;right++,left++){
        x1=fc(left);
        x2=fc(right);
        if(!x1){
            printf("%.2lf",left);
            cnt++;
        }
        if(x1*x2<0){
        while(right-left>=0.001){
            mid=(right+left)/2;
            if(fc(mid)*fc(right)<=0) left=mid;
            else right=mid;
            }
            printf("%.2lf ",left);
            cnt++;
        }
        if(cnt==3) break;
    }
    return 0;
}