View Compilation Error

0_0_2046332_8146.cpp: In function `int main()':
0_0_2046332_8146.cpp:6: error: `n' undeclared (first use this function)
0_0_2046332_8146.cpp:6: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_2046332_8146.cpp:6: error: `sort' undeclared (first use this function)
0_0_2046332_8146.cpp:13: error: `x1' undeclared (first use this function)
0_0_2046332_8146.cpp:14: error: `y1' undeclared (first use this function)
0_0_2046332_8146.cpp:15: error: `x2' undeclared (first use this function)
0_0_2046332_8146.cpp:16: error: `y2' undeclared (first use this function)
0_0_2046332_8146.cpp:21: error: `t' undeclared (first use this function)