View Compilation Error

944791_0_0_6473.cpp:4: error: `main' must return `int'
944791_0_0_6473.cpp: In function `int main(...)':
944791_0_0_6473.cpp:7: error: `a' undeclared (first use this function)
944791_0_0_6473.cpp:7: error: (Each undeclared identifier is reported only once for each function it appears in.)
944791_0_0_6473.cpp:7: error: `b' undeclared (first use this function)