switch-case error | the value of is not usable in a constant expression

I wrote a simple example to solve the problems I faced when writing his program.

During program execution I get values of input1 and input2 when returning values from functions, which are then never change. Then a little later after various computations in the process of the program I get a result which is also no longer changeable.

I'm trying to compare them using switch-case, but I get one error "the value of ‘input1’ is not usable in a constant expression".

#include <iostream>

using namespace std;

char getChar()
{
    char c;
    cin >> c;
    return c;
}

int main()
{
    // it doesn't work
    const char input1 = getChar();
    const char input2 = getChar();

    // it it works
    //const char input1 = 'R';
    //const char input2 = 'X';

    char result = getChar();
    switch(result)
    {
        case input1:
            cout << "input1" << endl;
            break;
        case input2:
            cout << "input2" << endl;
            break;
    }
    return 0;
}