/in/foo.c: In function 'main':
/in/foo.c:6:8: warning: too many arguments for format [-Wformat-extra-args]
  scanf("%f",&a,&b);
        ^~~~
/in/foo.c:9:13: warning: format '%d' expects argument of type 'int', but argument 2 has type 'double' [-Wformat=]
  printf("V=%d\n",V);
             ^
/in/foo.c:7:6: warning: 'Pl' is used uninitialized in this function [-Wuninitialized]
  S=Pl*a*a;
    ~~^~