foo.cc: In function 'void fun(int, int)':
foo.cc:22:5: warning: unused variable 'i' [-Wunused-variable]
 int i;
     ^
foo.cc: In function 'int main()':
foo.cc:33:9: warning: unused variable 'i' [-Wunused-variable]
 int k=0,i,j,a;
         ^
foo.cc:33:11: warning: unused variable 'j' [-Wunused-variable]
 int k=0,i,j,a;
           ^
foo.cc:34:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&n);
 ~~~~~^~~~~~~~~
foo.cc:35:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&a);
 ~~~~~^~~~~~~~~

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