ITP exceptions 1 my

#include <iostream>
#include <string>

using namespace std;

class LengthsNotEqualException : public exception
{
public:
    LengthsNotEqualException() {}

    const char* what() const noexcept {
        return "The lengths of two containers are not equal";
    }
};

class Container {
private:
    int size;
    int* array;

public:
    Container() {
        size = 0;
        array = NULL;
    }

    friend istream& operator >> (istream& cin, Container& now) {
        cin >> now.size;
        now.array = new int[now.size];
        for (int i = 0; i < now.size; i++)
            cin >> now.array[i];
        return cin;
    }

    friend ostream& operator << (ostream& cout, Container now) {
        for (int i = 0; i < now.size; i++)
            cout << now.array[i];
        return cout;
    }

    friend int dot_product(Container, Container);
};

int dot_product(Container first, Container second) {
    int result = 0;
    if (first.size != second.size)
        throw LengthsNotEqualException();

    for (int i = 0; i < first.size; i++)
        result += first.array[i] * second.array[i];
    return result;
}

int main()
{
    Container first, second;
    int size;

    cin >> first >> second;

    try {
        cout << dot_product(first, second);
    }
    catch (LengthsNotEqualException & exception){
        cout << exception.what();
    }
}