View Compilation Error

0_0_10015489_31503.cpp: In function `int main()':
0_0_10015489_31503.cpp:4: error: `i' undeclared (first use this function)
0_0_10015489_31503.cpp:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_10015489_31503.cpp:6: error: `sum' cannot be used as a function
0_0_10015489_31503.cpp:10: error: `sum' cannot be used as a function