/in/foo.cc: In function 'int main()':
/in/foo.cc:10:9: warning: iteration 10 invokes undefined behavior [-Waggressive-loop-optimizations]
 { if(a[k]-30<=i)
      ~~~^
/in/foo.cc:9:10: note: within this loop
 for(k=0;k<=10;k++)
         ~^~~~
/in/foo.cc:10:3: warning: 'i' is used uninitialized in this function [-Wuninitialized]
 { if(a[k]-30<=i)
   ^~