foo.cc: In function ‘int main()’:
foo.cc:38:15: warning: ‘ans’ may be used uninitialized [-Wmaybe-uninitialized]
   38 |         printf("%.3f",ans);
      |         ~~~~~~^~~~~~~~~~~~
foo.cc:18:24: note: ‘ans’ was declared here
   18 |         double l=0,r=0,ans;
      |                        ^~~