/in/foo.cc: In function 'int main()':
/in/foo.cc:75:39: warning: format '%lf' expects argument of type 'double*', but argument 2 has type 'long double*' [-Wformat=]
  for(int i=1;i<=n;++i) scanf("%lf",x+i);
                                       ^
/in/foo.cc:76:39: warning: format '%lf' expects argument of type 'double*', but argument 2 has type 'long double*' [-Wformat=]
  for(int i=1;i<=n;++i) scanf("%lf",y+i);
                                       ^
/in/foo.cc:100:20: warning: format '%lf' expects argument of type 'double', but argument 2 has type 'long double' [-Wformat=]
  printf("%.3lf",ans);
                    ^