#include <iostream>

using namespace std;

void multiply(double V[], double A[][], double result[], int N)
{ for (int i = 0; i < N; i += 1)
  { result[i] = 0;
    for (int j = 0; j < N; j += 1)
      result[i] += V[i] * A[i][j]; } }

void print(double V[], int N)
{ for (int i = 0; i < N; i += 1)
    cout << V[i] << "\t";
  cout << "\n"; }

void multiply(double A[][], double B[][], double Result[][], int N)
{ for (int i = 0; i < N; i += 1)
    for (int j = 0; j < N; j += 1)
    { Result[i][j] = 0;
      for (int k = 0; k < N; k += 1)
        Result[i][j] += A[i][k] * B[k][j]; } }

void print(double M[][], int N)
{ for (int i = 0; i < N; i += 1)
  { for (int j = 0; j < N; j += 1)
      cout << M[i][j] << "\t";
    cout << "\n"; } }

int main()
{ double x[4][4] = { { 1, 0, 3, -2 }, { 0, -1, 0, 1 }, { 2, -3, 0, 1 }, { 1, 1, 1, 1 } };
  double y[4][4] = { { 0, 1, 3, 1 }, { 2, 1, 0, 0 }, { -3, 1, -2, 0 }, { 1, -2, -1, -1 } };
  double product[4][4];
  double input[4] = { 1.231, 2.94, -1.66, 1 };
  double output[4];

  multiply(x, y, product, 4);
  print(product, 4);
  cout << "\n";
  multiply(input, product, output, 4);
  print(output, 4);
  cout << "\n"; }