View Compilation Error

0_0_2316818_21392.cpp: In function `int main()':
0_0_2316818_21392.cpp:11: error: `A' undeclared (first use this function)
0_0_2316818_21392.cpp:11: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_2316818_21392.cpp:12: error: `B' undeclared (first use this function)
0_0_2316818_21392.cpp:13: error: `C' undeclared (first use this function)
0_0_2316818_21392.cpp:14: error: `D' undeclared (first use this function)
0_0_2316818_21392.cpp:15: error: `E' undeclared (first use this function)
0_0_2316818_21392.cpp:16: error: `F' undeclared (first use this function)