foo.cc: In function 'int main()':
foo.cc:21:16: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     int n;scanf("%d",&n);
           ~~~~~^~~~~~~~~
foo.cc:24:11: warning: ignoring return value of 'int system(const char*)', declared with attribute warn_unused_result [-Wunused-result]
     system("pause");
     ~~~~~~^~~~~~~~~

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