Memory Leak!

class Expression
{
public:
    virtual double eval() = 0;
};

class FE: public Expression
{
public:
    FE * expr = nullptr;
    FE(FE* expr1) : expr(expr1) { }
    double eval()
    {
        return 1;
    }
    ~FE()
    {
        delete expr;
    }
};


int main()
{
    FE * expr = new FE(nullptr);
    {
        for (int i = 0; i < 5000; i++)
        {
            expr = new FE(expr);
        }
    }
    delete expr;
    return 0;
}