View Compilation Error

270167_0_3615.cpp: In function `int main()':
270167_0_3615.cpp:58: error: `x1' undeclared (first use this function)
270167_0_3615.cpp:58: error: (Each undeclared identifier is reported only once for each function it appears in.)
270167_0_3615.cpp:58: error: `y1' undeclared (first use this function)
270167_0_3615.cpp:58: error: `x2' undeclared (first use this function)
270167_0_3615.cpp:58: error: `y2' undeclared (first use this function)
270167_0_3615.cpp:58: error: `x3' undeclared (first use this function)
270167_0_3615.cpp:58: error: `y3' undeclared (first use this function)
270167_0_3615.cpp:58: error: `x4' undeclared (first use this function)
270167_0_3615.cpp:58: error: `y4' undeclared (first use this function)