static int operatorsrequired(unsigned long long v, unsigned long long *a, size_t n, int minop) {
    // assumes no unsigned long long overflowing
    if (n == 1) {
        if (v == *a) return minop;
        return 0;
    }
    unsigned long long tmp = a[1];
    int pplus, pmult, pconcat = 0;
    a[1] = a[0] + tmp;
    int p = operatorsrequired(v, a+1, n-1, (minop > 2)?3:2);
    pplus = operatorsrequired(v, a+1, n-1, 2);
    a[1] = tmp;
    if (p) return p;
    a[1] = a[0] * tmp;
    p = operatorsrequired(v, a+1, n-1, (minop > 2)?3:2);
    pmult = operatorsrequired(v, a+1, n-1, 2);
    a[1] = tmp;
    if (p) return p;
    a[1] = concat(a[0], tmp);
    p = operatorsrequired(v, a+1, n-1, 3);
    a[1] = tmp;
    return p;
    if (!pplus && !pmult) {
        a[1] = concat(a[0], tmp);
        pconcat = operatorsrequired(v, a+1, n-1, 3);
        a[1] = tmp;
    }
    if (pconcat) return 3;
    if (pmult) return 2;
    if (pplus) return 2;
    return 0;
}

void aoc202407(char *data, size_t len) {
    (void)len; // unused argument
    unsigned long long calibrationtotal = 0, calibration3total = 0;
    char *line = strtok(data, "\n");
    unsigned long long number[50], nnumber;