View Compilation Error

0_0_28615912_3505.cpp: In function 'int main(int)':
0_0_28615912_3505.cpp:14:26: error: 'scanf' was not declared in this scope
     for (; scanf("%d", &a), a >= 0; ) {
                          ^
0_0_28615912_3505.cpp:24:25: error: 'printf' was not declared in this scope
         printf("%d\n", a);
                         ^