UVA 10250 The Other Two Trees

#include <cstdio>#include <cmath>int main() {double x1, y1, x2, y2;double x3, y3, x4, y4;double a, b;while (scanf("%lf%lf%lf%lf", &x1, &y1, &x2, &y2) != EOF) {if (fabs(x1 - x2) < 1e-8 && fabs(y1 - y2) < 1e-8) {printf("Impossible.\n");continue;}a = (y1 - y2 + (x2 - x1)) / 2; b = (y1 - y2 - (x2 - x1)) / 2;x3 = x1 + a;x4 = x1 - b;y3 = y1 - b;y4 = y1 - a;printf("%.10lf %.10lf %.10lf %.10lf\n", x3, y3, x4, y4);}return 0;}