View Compilation Error

0_0_7706869_5946.cpp:2: error: `_int64' does not name a type
0_0_7706869_5946.cpp: In function `int main()':
0_0_7706869_5946.cpp:6: error: `f' undeclared (first use this function)
0_0_7706869_5946.cpp:6: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_7706869_5946.cpp:9: error: `sum' undeclared (first use this function)