foo.cc: In function 'int main()':
foo.cc:7:18: warning: 'a' is used uninitialized [-Wuninitialized]
    7 |         while(a[s]!=-1)
      |               ~~~^
foo.cc:5:16: note: 'a' declared here
    5 |         double a[10001],sum=0;
      |                ^

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