Operator overloading mistake '+'

#include <cstdlib>
#include <iostream>
#include <vector>
#include <cmath>

using namespace std;

class Overload {
public:
    Overload();
    Overload(int);
    
    Overload operator+(Overload &) ;
    void SetK(int k);
    int GetK() const;
    void SetVect(vector<double> vect);
    vector<double> GetVect() const;
    
   
    
private:
    vector<double> vect ;
    int k ;
    

};


int main(int argc, char** argv) {
    
    Overload a,b(10),c(10) ;
    a= b+c ;
    
    cout <<"\nAdded :\n" ;
    for(unsigned int i=0;i<a.GetVect().size(); ++i)
    cout <<"Res : " << a.GetVect()[i] << endl ;   
    cout << "first element : "<< a.GetVect()[0] << endl ; 
    return 0;
}


Overload::Overload() {
    k=10 ;
    cout << "\nFrist Started\n" ;
    for(unsigned int i=0;i<k ; ++i){
        double res = 1/pow(i,2) ;
        vect.push_back(res);
        cout << vect[i] << " " ;
    }
    cout << "VEctor size : " << vect.size() << endl ;
    cout <<"\nfirst ended\n"<< endl ;
}

Overload::Overload(int k) {
    double res=0 ;
    cout << "\nsecond started : \n" ;
    for(unsigned int i=0;i<k ; ++i){
        res = 1/pow(i,2) ;
        vect.push_back(res);
        cout << vect[i] << " " ;
    }
    cout << "\nsecond ended : \n" ;
}

Overload Overload::operator+(Overload &a){
    double res=0 ;
    Overload x ;
    for(unsigned int i=0 ;i<vect.size();i++) {
        res = vect[i] + a.vect[i];
        x.vect.push_back(res) ;
    }
    return x ;
}

void Overload::SetK(int k) {
    this->k = k;
}

int Overload::GetK() const {
    return k;
}

void Overload::SetVect(vector<double> vect) {
    this->vect = vect;
}

vector<double> Overload::GetVect() const {
    return vect;
}