foo.cc: In function 'int main()':
foo.cc:22:25: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::vector<int>::size_type {aka long unsigned int}' [-Wformat=]
  printf("%d\n", v.size());
                 ~~~~~~~~^
foo.cc:17:15: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   int x; scanf("%d", &x);
          ~~~~~^~~~~~~~~~

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