题解 | 绕距

#include <iostream>
#include <cmath>
#include <iomanip>

using namespace std;

int main() {
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    double de = sqrt((a - c) * (a - c) + (b - d) * (b - d));
    double dm = abs(a - c) + abs(b - d);
    cout << fixed << setprecision(10) <<abs(de - dm) << endl;
    return 0;
}
// 64 位输出请用 printf("%lld")