View Compilation Error

0_0_16283013_5584.cpp: In function 'int main()':
0_0_16283013_5584.cpp:5:2: error: expected initializer before 'long'
  long long sum;
  ^
0_0_16283013_5584.cpp:6:20: error: 'n' was not declared in this scope
  while(scanf("%d",&n)!=EOF)
                    ^
0_0_16283013_5584.cpp:8:3: error: 'sum' was not declared in this scope
   sum=n*(n+1)/2;
   ^