foo.cc: In function 'int main()':
foo.cc:5:8: warning: unused variable 'w' [-Wunused-variable]
    5 |  int n,w;
      |        ^
foo.cc:16:8: warning: ignoring return value of 'int system(const char*)', declared with attribute warn_unused_result [-Wunused-result]
   16 |  system("pause");
      |  ~~~~~~^~~~~~~~~

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