#include <stdio.h>

const double PI = 3.14159265359;
double indozou(double h, double r)
{
    double maeashi_ensyu = 2 * PI * r;
    return -8.245 + 6.807 * h + 7.073 * maeashi_ensyu;
}

int main(void)
{
    double h, r;
    scanf("%lf %lf", &h, &r);
    printf("%lf\n", indozou(h, r));
    return 0;
}