View Compilation Error

0_0_2963628_1863.cpp:7: error: `_int64' does not name a type
0_0_2963628_1863.cpp: In function `int main()':
0_0_2963628_1863.cpp:43: error: `sum' undeclared (first use this function)
0_0_2963628_1863.cpp:43: error: (Each undeclared identifier is reported only once for each function it appears in.)