View Compilation Error

0_0_9327911_19633.cpp: In function `int main()':
0_0_9327911_19633.cpp:4: error: `A' undeclared (first use this function)
0_0_9327911_19633.cpp:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_9327911_19633.cpp:4: error: `B' undeclared (first use this function)
0_0_9327911_19633.cpp:4: error: `F' undeclared (first use this function)