#include <stdio.h>

int main() {
    double a = 0.0;
    double p = 0.0;
    double b = 0.0;
    double t = 1.0;

    for (int d = 1; d <= 10; d++) {
        b = 0.0;  // ← これが必須

        while (b < 2.0) {
            p = a;
            a = a + t;
            b = a * a;
        }

        a = p;        // 行き過ぎた分を戻す
        t = t / 10.0;
    }

    printf("%.10f\n", a);
    return 0;
}