foo.c: In function 'main':
foo.c:3:5: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    3 |     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:3:5: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    3 |     scanf("%d%d",&a,&b);
      |     ^~~~~
foo.c:3:5: note: include '<stdio.h>' or provide a declaration of 'scanf'
foo.c:4:5: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    4 |     printf("%d",a+b);
      |     ^~~~~~
foo.c:4:5: note: include '<stdio.h>' or provide a declaration of 'printf'
foo.c:4:5: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
foo.c:4:5: note: include '<stdio.h>' or provide a declaration of 'printf'

[Hydro](https://hydro.ac)提供评测服务