foo.cc: In function 'int main()':
foo.cc:5:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
 #define file(s) freopen(s".in","r",stdin),freopen(s".out","w",stdout)
                 ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:30:9: note: in expansion of macro 'file'
         file("s");
         ^~~~
foo.cc:5:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
 #define file(s) freopen(s".in","r",stdin),freopen(s".out","w",stdout)
                 ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:30:9: note: in expansion of macro 'file'
         file("s");
         ^~~~
foo.cc:32:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%lf",&n,&Eu);
     ~~~~~^~~~~~~~~~~~~~~~
foo.cc:33:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     fp(i,1,n)scanf("%lf%lf%lf",s+i,k+i,v+i);
              ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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