/in/foo.cc: In function 'int main()':
/in/foo.cc:6:10: warning: unused variable 'k' [-Wunused-variable]
  int i=1,k=0,b[200010],n;
          ^
/in/foo.cc:10:7: warning: iteration 200010 invokes undefined behavior [-Waggressive-loop-optimizations]
   b[i]=i;
   ~~~~^~
/in/foo.cc:8:15: note: within this loop
  for(int i=0;i<=200010;i++)
              ~^~~~~~~~