View Compilation Error

0_0_31915950_16836.cpp:6:11: error: '::main' must return 'int'
 void main()
           ^
0_0_31915950_16836.cpp: In function 'int main()':
0_0_31915950_16836.cpp:10:25: error: 'scanf_s' was not declared in this scope
  while (scanf_s("%d", &n),n!=0){
                         ^
0_0_31915950_16836.cpp:14:25: error: 'memset' was not declared in this scope
   memset(a, 0, sizeof(a)); 
                         ^