View Compilation Error

0_0_6149900_21466.cpp: In function `int main()':
0_0_6149900_21466.cpp:15: error: `A' undeclared (first use this function)
0_0_6149900_21466.cpp:15: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_6149900_21466.cpp:16: error: `B' undeclared (first use this function)
0_0_6149900_21466.cpp:17: error: `C' undeclared (first use this function)
0_0_6149900_21466.cpp:18: error: `D' undeclared (first use this function)
0_0_6149900_21466.cpp:19: error: `E' undeclared (first use this function)
0_0_6149900_21466.cpp:20: error: `F' undeclared (first use this function)