View Compilation Error

27739_0_5228.cpp:3: error: `_int64' does not name a type
27739_0_5228.cpp: In function `int main()':
27739_0_5228.cpp:10: error: `_int64' undeclared (first use this function)
27739_0_5228.cpp:10: error: (Each undeclared identifier is reported only once for each function it appears in.)
27739_0_5228.cpp:10: error: expected `;' before "n"
27739_0_5228.cpp:11: error: `n' undeclared (first use this function)
27739_0_5228.cpp:12: error: `sum' undeclared (first use this function)