View Compilation Error

0_0_10221717_12974.cpp: In function `int merge_sort(int, int)':
0_0_10221717_12974.cpp:24: error: `p' undeclared (first use this function)
0_0_10221717_12974.cpp:24: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_10221717_12974.cpp:24: error: `m' undeclared (first use this function)