View Compilation Error

1_868_5019_14932.cpp: In function 'int main(int, const char**)':
1_868_5019_14932.cpp:9:14: error: 'y' was not declared in this scope
 printf("%d",(y*y-x*x)/4);
              ^
1_868_5019_14932.cpp:9:18: error: 'x' was not declared in this scope
 printf("%d",(y*y-x*x)/4);
                  ^