View Compilation Error

0_0_24945994_11124.cpp:3:1: error: 'll' does not name a type
 ll a,b;
 ^
0_0_24945994_11124.cpp: In function 'int main()':
0_0_24945994_11124.cpp:5:27: error: 'a' was not declared in this scope
  while(~scanf("%lld%lld",&a,&b)) printf("%lld\n",(a+b)/2);
                           ^
0_0_24945994_11124.cpp:5:30: error: 'b' was not declared in this scope
  while(~scanf("%lld%lld",&a,&b)) printf("%lld\n",(a+b)/2);
                              ^