foo.c: In function 'main':
foo.c:17:5: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
   17 |     scanf("%d", &n);
      |     ^~~~~
foo.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | int countWays(int n) {
foo.c:17:5: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
   17 |     scanf("%d", &n);
      |     ^~~~~
foo.c:17:5: note: include '<stdio.h>' or provide a declaration of 'scanf'
foo.c:19:5: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   19 |     printf("%d\n", ways);
      |     ^~~~~~
foo.c:19:5: note: include '<stdio.h>' or provide a declaration of 'printf'
foo.c:19:5: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
foo.c:19:5: note: include '<stdio.h>' or provide a declaration of 'printf'

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