OJ Board

in past topics ,it had talked about using "Unsigned Long Long" Data type for GCC
but when i write
unsigned long long ull = 0xffffffffffffffff; // 18446744073709551615
//a 64 bit value

it arises a compiler error : Integer Constant Out of range

should I set something at my code or for compiler?

I have extracted this from the manual for you:

To make an integer constant of type `long long int', add the suffix `LL' to the integer. To make an integer constant of type `unsigned long long int', add the suffix `ULL' to the integer.