#include <cmath> #include <iostream> using namespace std; int main() { int n = 2; double x1, y1, x2, y2; cin >> x1 >> y1 >> x2 >> y2; double c = sqrt((x1 - x2)*(x1 - x2) + (y1 - y2) * (y1 - y2)); double d = fabs(x1 - x2) + fabs(y1 - y2); double e = fabs(d - c); printf("%.9lf", e); return 0; } // 64 位输出请用 printf("%lld")