double probks(double alam)
{
	double eps1 = 0.001;
    double eps2 = 0.00000001;
    double a2 = -2.0 * alam * alam;
    double fac = 2.0;
    double aaa,temp = 0.0;
    double term,termbf = 0.0;
    for (int j = 1; j<=100; j++)
	{
        term = fac * exp(a2 * j * j);
        temp = temp + term;
        aaa = fabs(term);
        if (aaa < eps1 * termbf || aaa < eps2 * temp)
		{
			return temp;
        }
        fac = -fac;
        termbf = fabs(term);
    }
    return 1.0;
}