C++ code used for Stack Overflow qeustoin

#include "stdafx.h"
#include <iostream>
using namespace std;

void CtoF() {// c to f furmula
    double input;
    cout << "Enter a number[Celsius-Fahrenheit]" << endl;
    cin >> input;
    cout << "it's " << input * 1.8 + 32 << " Fahrenheit " << endl;
    return;
}
void CtoK() {// c to k  furmula
    double input;
    cout << "Enter a number[Celsius-Kelvin]" << endl;
    cin >> input;
    cout << "it's " << input + 273.15   << " Kelvin " << endl;
    return;
}
void FtoC() {//f to c furmula
    double input;
    cout << "Enter a number[Fahrenheit-Celsius]" << endl;
    cin >> input;
    cout << "it's " << input / 1.8 - 32 << " Celsius " << endl;

}
void FtoK() {//f to k furmula
    double input;
    cout << "Enter a number[Fahrenheit-Kelvin]" << endl;
    cin >> input;
    cout << "it's " << input / 1.8 - 32 + 273.15 << " Kelvin " << endl;
    return;
}
void KtoF() {// k to f furmula
    double input;
    cout << "Enter a number[Kelvin-Fahrenheit]" << endl;
    cin >> input;
    cout << "it's " << (input - 273.15) * 1.8 + 32 << " Fahrenheit " << endl;

}
void KtoC() {// k to c furmula
    double input;
    cout << "Enter a number[Kelvin-Celsius]" << endl;
    cin >> input;
    cout << "it's " <<273.15 - input << " Celsius " << endl;
}
void whatToWhat(char firstDegrees, char secondDegrees) {
    if (firstDegrees == 'C' || 'c') {// tests if the user want form c to f
        if (secondDegrees == 'F' || 'f') {
            CtoF();
        }
    }if (firstDegrees == 'C' || 'c') {// tests if the user want form c to k
        if (secondDegrees == 'K' || 'k') {
            CtoK();
        }
    }if (firstDegrees == 'F' || 'f') {// tests if the user want form f to c
        if (secondDegrees == 'C' || 'c') {
            FtoC();
        }
    }if (firstDegrees == 'F' || 'f') {// tests if the user want form f to k
        if (secondDegrees == 'K' || 'k') {
            FtoK();
        }
    }if (firstDegrees == 'K' || 'k') {// tests if the user want form k to f
        if (secondDegrees == 'F' || 'f') {
            KtoF();
        }
    }if (firstDegrees == 'K' || 'k') {// tests if the user want form k to c
        if (secondDegrees == 'C' || 'c') {
            KtoC();
        }
    }

}
    int main() {
    char firstDegrees, secondDegrees;

    cout << "enter what you want to convert to what[C, K, F]" << endl;
    cin >> firstDegrees;
    cout << "to" << endl;
    cin >> secondDegrees;
    whatToWhat(firstDegrees, secondDegrees);

    return 0;
}