foo.cc: In function 'int main()':
foo.cc:101:15: warning: 'na' is used uninitialized in this function [-Wuninitialized]
  for(int i=1;i<=na;i++){
              ~^~~~
foo.cc:99:11: warning: 'nb' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int n,na,nb;
           ^~
foo.cc:99:6: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int n,na,nb;
      ^

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