View Compilation Error

0_0_7842299_28532.cpp: In function `int main()':
0_0_7842299_28532.cpp:4: error: `_int64' undeclared (first use this function)
0_0_7842299_28532.cpp:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_7842299_28532.cpp:4: error: expected `;' before "a"
0_0_7842299_28532.cpp:5: error: `n' undeclared (first use this function)
0_0_7842299_28532.cpp:6: error: `i' undeclared (first use this function)
0_0_7842299_28532.cpp:8: error: `a' undeclared (first use this function)
0_0_7842299_28532.cpp:8: error: `b' undeclared (first use this function)
0_0_7842299_28532.cpp:9: error: `sum' undeclared (first use this function)