foo.cc:14:0: warning: ignoring #pragma GCC opitmize [-Wunknown-pragmas]
 #pragma GCC opitmize(3)
 
foo.cc: In function 'int main()':
foo.cc:25:22: warning: format '%d' expects argument of type 'int*', but argument 2 has type 'long long int*' [-Wformat=]
         scanf("%d",&n);
                    ~~^
foo.cc:25:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&n);
         ~~~~~^~~~~~~~~

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