foo.cc: In function 'int main()':
foo.cc:33:17: warning: unused variable 't' [-Wunused-variable]
    int tot = 0, t;
                 ^
foo.cc:20:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen("1.in", "r", stdin);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~
foo.cc:21:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen("1.out", "w", stdout);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:23:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~

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