View Compilation Error

0_0_11416982_13739.cpp: In function `bool check(ll, ll)':
0_0_11416982_13739.cpp:69: error: `x' undeclared (first use this function)
0_0_11416982_13739.cpp:69: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_11416982_13739.cpp:71: error: `y' undeclared (first use this function)