foo.cc: In function 'int main()':
foo.cc:5:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&W,&n);
   ~~~~~^~~~~~~~~~~~~~
foo.cc:7:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&a[i]);
     ~~~~~^~~~~~~~~~~~

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