foo.cc:4: warning: ignoring #pragma gcc optimize [-Wunknown-pragmas]
    4 | #pragma gcc optimize(2)
      | 
foo.cc: In function 'int main()':
foo.cc:50:6: warning: unused variable 'sc' [-Wunused-variable]
   50 |  int sc=1<<bits;
      |      ^~

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