foo.c: In function 'output':
foo.c:20:3: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   20 |   printf("%d ", a[i]);
      |   ^~~~~~
foo.c:20:3: warning: incompatible implicit declaration of built-in function 'printf'
foo.c:2:1: note: include '<stdio.h>' or provide a declaration of 'printf'
    1 | #include <math.h>
  +++ |+#include <stdio.h>
    2 | 
foo.c:22:2: warning: incompatible implicit declaration of built-in function 'printf'
   22 |  printf("\n");
      |  ^~~~~~
foo.c:22:2: note: include '<stdio.h>' or provide a declaration of 'printf'
foo.c: In function 'main':
foo.c:26:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
   26 |  scanf("%d %d", &n1, &n2);
      |  ^~~~~
foo.c:26:2: warning: incompatible implicit declaration of built-in function 'scanf'
foo.c:26:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
foo.c:39:2: warning: incompatible implicit declaration of built-in function 'printf'
   39 |  printf("%d %d", A, B);
      |  ^~~~~~
foo.c:39:2: note: include '<stdio.h>' or provide a declaration of 'printf'

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