View Compilation Error

0_0_4938042_28892.cpp: In function `int main()':
0_0_4938042_28892.cpp:9: error: `A' undeclared (first use this function)
0_0_4938042_28892.cpp:9: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_4938042_28892.cpp:9: error: expected `;' before "d"