View Compilation Error

0_0_23320116_15947.cpp:2:11: error: '::main' must return 'int'
 void main() {
           ^
0_0_23320116_15947.cpp: In function 'int main()':
0_0_23320116_15947.cpp:7:39: error: 'scanf_s' was not declared in this scope
  scanf_s("%c%c%c", &a, 1, &b, 1, &c, 1);
                                       ^