View Compilation Error

0_0_7750996_7321.cpp:11: error: `_int64' does not name a type
0_0_7750996_7321.cpp: In function `int main()':
0_0_7750996_7321.cpp:21: error: `sum' undeclared (first use this function)
0_0_7750996_7321.cpp:21: error: (Each undeclared identifier is reported only once for each function it appears in.)