View Compilation Error

267482_0_2838.cpp:11: error: `main' must return `int'
267482_0_2838.cpp: In function `int main(...)':
267482_0_2838.cpp:16: error: `sum' undeclared (first use this function)
267482_0_2838.cpp:16: error: (Each undeclared identifier is reported only once for each function it appears in.)