View Compilation Error

0_0_4140487_23287.c: In function `main':
0_0_4140487_23287.c:98: error: `top' undeclared (first use in this function)
0_0_4140487_23287.c:98: error: (Each undeclared identifier is reported only once
0_0_4140487_23287.c:98: error: for each function it appears in.)
0_0_4140487_23287.c:98: error: `y' undeclared (first use in this function)
0_0_4140487_23287.c:98: error: `x' undeclared (first use in this function)