C++出现：error: passing 'const Employee' as 'this' argument of 'int Employee::getSalary()' discards qualifiers [-fpermissive]

#include <iostream>
#include <map>
#include <string>
#include <ctime>

#define MAX 10

using namespace std;

class Employee{
public:
    string m_Name;
    Employee(string name, int salary)
    {
        this->m_Name = name;
        this->m_Salary = salary;
    }
    void setSalary(int salary)
    {
        this->m_Salary = salary;
    }
    int getSalary()
    {
        return this->m_Salary;
    }
private:
    int m_Salary;
};
class MyCompare{
public:
    bool operator()(const Employee &p1, const Employee &p2) const
    {
        return p1.getSalary() > p2.getSalary();
    }
};
void printEmployee(const multimap<int, Employee, MyCompare> &mp)
{

}
int main(void)
{

    cout << rand() / RAND_MAX << endl;

    return 0;
}