View Compilation Error

0_0_19429473_10282.cpp:2:10: error: #include expects "FILENAME" or <FILENAME>
 #include namespace std;
          ^
0_0_19429473_10282.cpp: In function 'int main()':
0_0_19429473_10282.cpp:8:21: error: 'scanf' was not declared in this scope
  while(scanf("%d",&n)!=EOF)
                     ^
0_0_19429473_10282.cpp:8:24: error: 'EOF' was not declared in this scope
  while(scanf("%d",&n)!=EOF)
                        ^
0_0_19429473_10282.cpp:15:4: error: 'flag' was not declared in this scope
    flag=0;
    ^
0_0_19429473_10282.cpp:34:20: error: 'printf' was not declared in this scope
   printf("%d\n",res);
                    ^