View Compilation Error

0_0_19841975_818.cpp:22:20: error: '_int64' has not been declared
 __int64 sum(int n, _int64 r,_int64 lb, _int64 rb)
                    ^
0_0_19841975_818.cpp:22:29: error: '_int64' has not been declared
 __int64 sum(int n, _int64 r,_int64 lb, _int64 rb)
                             ^
0_0_19841975_818.cpp:22:40: error: '_int64' has not been declared
 __int64 sum(int n, _int64 r,_int64 lb, _int64 rb)
                                        ^