#include <stdio.h>
#include <ctype.h>

enum state
{
    ST_START,
    ST_ESCAPE,
    ST_CSI,
    ST_FNKEY,
    ST_FNKEY_END
};

int main()
{
    int c = 0;
    enum state st = ST_START;
    int fn_num = 0;

    while ((c = getchar()) != EOF)
    {
        if (c == '\x1b')
            st = ST_ESCAPE;
        else if (c == '[' && st == ST_ESCAPE)
            st = ST_CSI;
        else if (st == ST_CSI && isdigit(c))
        {
            fn_num += 10 * (c - '0');
            st = ST_FNKEY;
        }
        else if (st == ST_FNKEY && isdigit(c))
        {
            fn_num += (c - '0');
            printf("FN key pressed, number: %d\n", fn_num);
            st = ST_FNKEY_END;
        }
        else if (st == ST_FNKEY_END && c == '~')
        {
            st = ST_START;
        }
        else
        {
            printf("Saw character: %c\n", c);
        }
    }
    return 0;
}