View Compilation Error

0_0_3036530_30104.cpp: In function `int cmp(const void*, const void*)':
0_0_3036530_30104.cpp:15: error: `pa' undeclared (first use this function)
0_0_3036530_30104.cpp:15: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_3036530_30104.cpp:16: error: `pb' undeclared (first use this function)