View Compilation Error

493611_0_0_9320.cpp: In function `int main()':
493611_0_0_9320.cpp:15: error: `a' undeclared (first use this function)
493611_0_0_9320.cpp:15: error: (Each undeclared identifier is reported only once for each function it appears in.)
493611_0_0_9320.cpp:15: error: `b' undeclared (first use this function)