double gaussKincaid(double b[], const double a[][4], int iterMax){

    double x[4] = {1.,1.,1.,1.};
    double estimatorVal = 1.;
    double reziduumVal = 1.;
    double x2[4];

    int k=0;
    while ((k<iterMax) && (fabs(estimatorVal)>=e) && (fabs(reziduumVal)>e)){

        for (int i=0;i<n;i++){
            x[i] = b[i];
            for (int j=0;j<n;j++){
                if(i!=j){
                    x[i] -= a[i][j]*x[j];
                }
            }
            x[i]/=a[i][i];
            x2[i] = x[i+1];
        }

		double x3[n];
    	for (int i=0; i<4;i++){
			x3[i] = fabs(x[i+1] - x2[i]);
		}

		double max = x3[0];
		for (int i=1;i<4;i++){
			if (x3[i] > max){
				max = x3[i];
			}
		}

		estimatorVal = max;

        std::cout << "\niteracja: " << k+1 << std::endl;

        for (int i=0;i<4;i++){
            std::cout << x[i] << " ";
        }

        reziduumVal = reziduum(x,b,a);
        std::cout << "\nestymator: " << estimatorVal
		//estimator(x2,x)
		<< " reziduum: " <<
        reziduumVal;
        std::cout << "\n";

        k++;
    }
}