View Compilation Error

0_0_26496597_23300.cpp: In function 'int main()':
0_0_26496597_23300.cpp:5:26: error: 'x1' was not declared in this scope
 while (scanf("%d%d%d%d",&x1,&y1,&x2,&x2)!=EOF)
                          ^
0_0_26496597_23300.cpp:5:30: error: 'y1' was not declared in this scope
 while (scanf("%d%d%d%d",&x1,&y1,&x2,&x2)!=EOF)
                              ^
0_0_26496597_23300.cpp:5:34: error: 'x2' was not declared in this scope
 while (scanf("%d%d%d%d",&x1,&y1,&x2,&x2)!=EOF)
                                  ^
0_0_26496597_23300.cpp:6:40: error: 'y2' was not declared in this scope
   printf("%0.2f\n",(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
                                        ^