/in/foo.cc: In function 'int main()':
/in/foo.cc:7:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(int i=a;i<=n-1;i++)
  ^~~
/in/foo.cc:21:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   cout<<ans;
   ^~~~