#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main()
{
    int note1,note2;
    double f,p;

while (1) {
    printf("Please enter first MIDI note (0-127): ");
    scanf("%d", &note1);
    if (note1 >= 0 && note1 <= 127)
        break;

                else
                        printf("The value entered was invalid. Try again.\n");
}

while (1) {
    printf("Please enter second MIDI note (0-127): ");
    scanf("%d", &note2);
    if (note2 >= 0 && note2 <= 127)
        break;
                else
                        printf("The value entered was invalid. Try again.\n");
}

    double f1, f2, exponent1, exponent2, difference;

    exponent1 = (note1 - 69)/12.0;
    exponent2 = (note2 - 69)/12.0;

    f1 = pow(2, exponent1) * 440;
    f2 = pow(2, exponent2) * 440;

    difference = f1 - f2;

    printf("The difference in frequencies is: %f Hz", difference);

    return 0;
}