foo.cc: In function 'int power(int, int, BigInt&)':
foo.cc:26:6: warning: unused variable 'cnt' [-Wunused-variable]
   26 |  int cnt=0;
      |      ^~~
foo.cc:52:1: warning: no return statement in function returning non-void [-Wreturn-type]
   52 | }
      | ^

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