View Compilation Error

0_0_35607724_29465.cpp:1:11: error: '::main' must return 'int'
 void main()
           ^
0_0_35607724_29465.cpp: In function 'int main()':
0_0_35607724_29465.cpp:4:21: error: 'scanf' was not declared in this scope
  while(scanf("%d",&n)!=EOF){
                     ^
0_0_35607724_29465.cpp:4:24: error: 'EOF' was not declared in this scope
  while(scanf("%d",&n)!=EOF){
                        ^
0_0_35607724_29465.cpp:7:23: error: 'printf' was not declared in this scope
    printf("%d\n\n",sum);
                       ^