View Compilation Error

0_0_29051141_12365.cpp:1:11: error: '::main' must return 'int'
 void main(){
           ^
0_0_29051141_12365.cpp: In function 'int main()':
0_0_29051141_12365.cpp:3:22: error: 'scanf' was not declared in this scope
   scanf("%d %d",&a,&b);
                      ^
0_0_29051141_12365.cpp:4:18: error: 'printf' was not declared in this scope
   printf("%d",a+b);
                  ^