foo.cc: In function 'int add_char(int, int)':
foo.cc:47:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
foo.cc: In function 'int main()':
foo.cc:76:25: warning: format '%d' expects argument of type 'int', but argument 2 has type 'll {aka long long int}' [-Wformat=]
 printf( "%I64d\n" , ans ) ;
                         ^
foo.cc:70:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf( "%d" , &n ) ;
 ~~~~~^~~~~~~~~~~~~

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