foo.cc: In function 'int main()':
foo.cc:32:11: warning: ignoring return value of 'int system(const char*)', declared with attribute warn_unused_result [-Wunused-result]
   32 |     system("pause");
      |     ~~~~~~^~~~~~~~~
foo.cc:25:5: warning: 'i' may be used uninitialized in this function [-Wmaybe-uninitialized]
   25 |     for (sum = 0; i > 0; i--)
      |     ^~~

[Hydro](https://hydro.ac)提供评测服务