foo.cc: In function 'void init()':
foo.cc:9:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 #define R(a) scanf("%d",&a)
              ~~~~~^~~~~~~~~
foo.cc:43:5: note: in expansion of macro 'R'
     R(n);
     ^
foo.cc:9:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 #define R(a) scanf("%d",&a)
              ~~~~~^~~~~~~~~
foo.cc:47:9: note: in expansion of macro 'R'
         R(x);
         ^

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