View Compilation Error

0_0_35277141_32684.cpp:3:12: error: '_int64' does not name a type
 #define LL _int64
            ^
0_0_35277141_32684.cpp:4:1: note: in expansion of macro 'LL'
 LL b[55];
 ^
0_0_35277141_32684.cpp:3:12: error: '_int64' does not name a type
 #define LL _int64
            ^
0_0_35277141_32684.cpp:5:1: note: in expansion of macro 'LL'
 LL fun(int n)
 ^
0_0_35277141_32684.cpp: In function 'int main()':
0_0_35277141_32684.cpp:17:16: error: 'fun' was not declared in this scope
   cout << fun(n) << endl;
                ^