foo.cc: In function 'int main()':
foo.cc:5:10: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int n,m,sum;
          ^~~
foo.cc:5:8: warning: 'm' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int n,m,sum;
        ^

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