#include <stdio.h>

const long double PI = 3.141592653589793238462643383;
long double indozou(long double h, long double r)
{
    long double maeashi_ensyu = 2 * PI * r;
    return (long double)-8.245 + 6.807 * h + 7.073 * maeashi_ensyu;
}

int main(void)
{
    long double h, r;
    scanf("%Lf %Lf", &h, &r);
    printf("%.12Lf\n", indozou(h, r));
    return 0;
}