foo.cc: In function 'int main()':
foo.cc:21:28: 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:15:21: 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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