View Compilation Error

0_0_11033684_8010.cpp: In function `int main()':
0_0_11033684_8010.cpp:21: error: `x1' undeclared (first use this function)
0_0_11033684_8010.cpp:21: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_11033684_8010.cpp:22: error: `x2' undeclared (first use this function)