foo.c: In function 'main':
foo.c:8:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  scanf("%d %d",&n1,&n2);
  ^~~~~
foo.c:8:2: warning: incompatible implicit declaration of built-in function 'scanf'
foo.c:8:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
foo.c:13:2: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
  printf("%d %d",c,d);
  ^~~~~~
foo.c:13:2: warning: incompatible implicit declaration of built-in function 'printf'
foo.c:13:2: note: include '<stdio.h>' or provide a declaration of 'printf'
/tmp/cchJS3yH.o: In function `main':
foo.c:(.text.startup+0x47): undefined reference to `input'
foo.c:(.text.startup+0x53): undefined reference to `input'
collect2: error: ld returned 1 exit status

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