foo.cpp: In function 'int main()':
foo.cpp:12:3: error: 'cin' was not declared in this scope
   cin>>a>>b;
   ^
foo.cpp:17:19: warning: unknown conversion type character 'l' in format [-Wformat=]
  printf("%lld\n",x);
                   ^
foo.cpp:17:19: warning: too many arguments for format [-Wformat-extra-args]