برنامه ی محاسبه ی مساحت مثلث با کمک محیط آن

float main()
{
float a,b,c,s,p;
printf("for calculating surface of triangle please insert the asked thing");
printf("\n\ninsert a:\n");
scanf("%f",&a);
printf("\n\ninsert b:\n");
scanf("%f",&b);
printf("\n\ninsert c:\n");
scanf("%f",&c);
p=(a+b+c)/2;
sqrt(s=p*(p-a)*(p-b)*(p-c));
printf("\n\n\nTHE Surface IS: ");
printf("%.2f",s);
getch();
}