View Compilation Error

0_0_19841957_490.cpp:22:1: error: '_int64' does not name a type
 _int64 sum(int n, _int64 r,_int64 lb, _int64 rb)
 ^
0_0_19841957_490.cpp: In function 'void output()':
0_0_19841957_490.cpp:55:40: error: 'sum' was not declared in this scope
  printf("%I64d\n", sum(N, R+1, S+1, E+1));
                                        ^