View Compilation Error

0_0_35227585_31215.cpp:2:11: error: '::main' must return 'int'
 void main()
           ^
0_0_35227585_31215.cpp: In function 'int main()':
0_0_35227585_31215.cpp:7:18: error: 'scanf_s' was not declared in this scope
   scanf_s("%d",&n);
                  ^