#include <iostream>
#include <fstream>
#include <cassert>

/*input file of first matrix*/
#define IN_FA "inputA.txt"

/*input file of second matrix*/
#define IN_FB "inputB.txt"

/*output file*/
#define OUT_F "output.txt"

using namespace std;

/*class Matrix*/
class Matrix {
    public:
        /*count of rows*/
        int n;

        /*count of columns*/
        int m;

        /*two-dimensional array*/
        int** data;

        /*function for allocating two-dimensional array*/
        void allocate() {
            data = new int* [n];

            for (int i = 0; i < n; i++)
                data[i] = new int [m];
        }

        /*function for destroying two-dimensional array*/
        void destroy() {
            return;
            if (n && m) {
                for (int i = 0; i < n; i++)
                    delete data[i];
                delete data;
            }
        }

    public:
        /*constructor by default*/
        Matrix() { n = m = 0; };

        /*initializer list constructors*/
        Matrix(int _n, int _m) : n(_n), m(_m) { allocate(); }

        /*destructor*/
        ~ Matrix() { destroy(); }

        /*function set. Reading matrix from file*/
        void set(string filename) {
            ifstream ifs(filename);

            assert(ifs && "File does not open!");

            ifs >> n >> m;

            destroy();
            allocate();

            for (int i = 0; i < n; i++)
                for (int j = 0; j < m; j++)
                    ifs >> data[i][j];
        }

        /*function get. Writing matrix to file*/
        void get(string filename) {
            ofstream ofs(filename);

            assert(ofs && "File does not created!");

            ofs << "n = " << n << " m = " << m << endl;
            ofs << "Matrix:" << endl;

            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++)
                    ofs << data[i][j] << " ";
                ofs << endl;
            }
        }

        /*assignation operator*/
        Matrix& operator = (const Matrix &x) {
            n = x.n; m = x.m;

            destroy();
            allocate();

            for (int i = 0; i < n; i++)
                for (int j = 0; j < m; j++)
                    data[i][j] = x.data[i][j];
            return *this;
        }

        /*multiplication operator*/
        Matrix operator * (const Matrix &x) { return mult(*this, x); }

        /*friend function for multiplication*/
        friend Matrix mult(const Matrix &a, const Matrix &b);
};

/*multiplication function*/
Matrix mult(const Matrix &a, const Matrix &b) {
    assert(a.m == b.n && "Matrices cannot be multiplied!");

    Matrix c(a.n, b.m);

    for (int i = 0; i < c.n; i++)
        for (int j = 0; j < c.m; j++) {
            c.data[i][j] = 0;
            for (int k = 0; k < a.m; k++)
                c.data[i][j] += a.data[i][k] * b.data[k][j];
        }
    return c;
}

int main() {

    Matrix a, b, c;

    /*reading from file*/
    a.set(IN_FA);

    b.set(IN_FB);

    /*calculating*/
    c = a * b;

    /*writing to file*/
    c.get(OUT_F);

    return 0;
}