/in/foo.cc: In function 'int main()':
/in/foo.cc:20:19: warning: too many arguments for format [-Wformat-extra-args]
  printf(".2lf",ans);
                   ^
/in/foo.cc:9:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j,n;
        ^
/in/foo.cc:10:9: warning: unused variable 'r' [-Wunused-variable]
  double r,a[111],b[111],ans=6.28;
         ^