View Compilation Error

216702_0_18718.cpp: In function `int main()':
216702_0_18718.cpp:13: error: `a' undeclared (first use this function)
216702_0_18718.cpp:13: error: (Each undeclared identifier is reported only once for each function it appears in.)
216702_0_18718.cpp:19: error: expected `}' at end of input