#include <iostream>
#include <cmath>
#include <iomanip>
 
using namespace std;
 
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
 
    int x, y;
    cin >> x >> y;
    double a = sqrt(5 * 5 + 5 * 5 - 4), // Tính đoạn OA
           c = sqrt((x - 5) * (x - 5) + (y - 5) * (y - 5) - 4), // Tính đoạn BK
           u = ((0 - 5) * (x - 5) + (0 - 5) * (y - 5)) // cos(OIK)
               / (sqrt(5 * 5 + 5 * 5) * sqrt((x - 5) * (x - 5) + (y - 5) * (y - 5))),
           v = 2 / sqrt((0 - 5) * (0 - 5) + (0 - 5) * (0 - 5)), // cos(OIA)
           w = 2 / sqrt((x - 5) * (x - 5) + (y - 5) * (y - 5)); // cos(BIK)
    double phi = (acos(u) - acos(v) - acos(w)), // Tính góc phi = OIK - OIA - BIK
           b = phi * 2; // Tính cung AB
    double res = a + b + c; // OA + cung AB + BK
    cout << fixed << setprecision(2) << res;
}

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