View Compilation Error

0_0_1929400_22052.c: In function `main':
0_0_1929400_22052.c:18: error: `A' undeclared (first use in this function)
0_0_1929400_22052.c:18: error: (Each undeclared identifier is reported only once
0_0_1929400_22052.c:18: error: for each function it appears in.)
0_0_1929400_22052.c:18: error: syntax error before '6'