View Compilation Error

0_0_2695516_28642.c: In function `main':
0_0_2695516_28642.c:54: error: `a' undeclared (first use in this function)
0_0_2695516_28642.c:54: error: (Each undeclared identifier is reported only once
0_0_2695516_28642.c:54: error: for each function it appears in.)
0_0_2695516_28642.c:54: error: `b' undeclared (first use in this function)