foo.cc: In function 'int power(int, int, BigInt&)':
foo.cc:13:6: warning: unused variable 'cnt' [-Wunused-variable]
   13 |  int cnt=0;
      |      ^~~
foo.cc:30:1: warning: no return statement in function returning non-void [-Wreturn-type]
   30 | }
      | ^
foo.cc:28:10: warning: 'i' is used uninitialized in this function [-Wuninitialized]
   28 |  for(int i; s<1000; s++,i++)
      |          ^

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