View Compilation Error

0_0_1325033_30850.cpp: In function `int main()':
0_0_1325033_30850.cpp:7: error: `_int64' undeclared (first use this function)
0_0_1325033_30850.cpp:7: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1325033_30850.cpp:7: error: expected `;' before "n"
0_0_1325033_30850.cpp:8: error: `n' undeclared (first use this function)
0_0_1325033_30850.cpp:9: error: `sum' undeclared (first use this function)
0_0_1325033_30850.cpp:10: error: `i' undeclared (first use this function)
0_0_1325033_30850.cpp:11: error: `num' undeclared (first use this function)