View Compilation Error

0_0_27685580_3957.cpp:3:11: error: '::main' must return 'int'
 void main()
           ^
0_0_27685580_3957.cpp: In function 'int main()':
0_0_27685580_3957.cpp:6:25: error: 'scanf_s' was not declared in this scope
  while (scanf_s("%d", &n)!=EOF){
                         ^