foo.c: In function 'main':
foo.c:4:9: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    4 |         scanf("%d%d", &a, &b);
      |         ^~~~~
foo.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | int main()
foo.c:4:9: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    4 |         scanf("%d%d", &a, &b);
      |         ^~~~~
foo.c:4:9: note: include '<stdio.h>' or provide a declaration of 'scanf'
foo.c:15:25: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   15 |                         printf("%d\n", a);
      |                         ^~~~~~
foo.c:15:25: note: include '<stdio.h>' or provide a declaration of 'printf'
foo.c:15:25: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
foo.c:15:25: note: include '<stdio.h>' or provide a declaration of 'printf'

[Hydro](https://hydro.ac)提供评测服务