View Compilation Error

0_0_13244077_10287.cpp:2:13: error: '_int64' was not declared in this scope
 double fact(_int64 x,_int64 y)
             ^
0_0_13244077_10287.cpp:2:22: error: '_int64' was not declared in this scope
 double fact(_int64 x,_int64 y)
                      ^
0_0_13244077_10287.cpp:2:30: error: expression list treated as compound expression in initializer [-fpermissive]
 double fact(_int64 x,_int64 y)
                              ^
0_0_13244077_10287.cpp:3:1: error: expected ',' or ';' before '{' token
 {
 ^