/in/foo.c: In function 'main':
/in/foo.c:41:11: warning: format '%f' expects argument of type 'float *', but argument 2 has type 'double *' [-Wformat=]
   scanf("%f%f",&a[i].a,&a[i].b);
           ^
/in/foo.c:41:13: warning: format '%f' expects argument of type 'float *', but argument 3 has type 'double *' [-Wformat=]
   scanf("%f%f",&a[i].a,&a[i].b);
             ^
/in/foo.c:33:6: warning: unused variable 'tt' [-Wunused-variable]
  int tt;
      ^~