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

#define natural unsigned short // csf sa mai pierd timp

int v[7]; //  the stack
void Init(natural k) { // initialzation function
    v[k] =  -1;
}
natural Succesor(natural k) {
    if (v[k] < 9) { // will generate the number until 9
        v[k]++;
        return 1;
    }
    return 0;
}

natural Valid(natural k) {
    natural i;
    if (v[k] % 2 == 1) return 1; // if is odd is valid
    for (i = 1; i < k; i++) // else we search if is a copy of number in vector
        if (v[i] == v[k])
            return 0; //if we fiind a copy is a invalid combination
    return 1;
}

natural valid2() { // we search if are exactly 3 numbers in vector
    natural nr = 0, i;
    for (i = 1; i <= 6; i++) {
        if (v[i] % 2 == 0) nr++;
    }

    if (nr != 3) return 0; // if are not 3 numbers in vector is an invlid case
    return 1;
}

natural Solution(natural k) {
    return (k == 6) && valid2(); // if we have 6 elements and 3 of them are disticnt even digits is a valid case
}

void Print() {
    natural i;
    printf("0721 "); // fixed digits
    for (i = 1; i <= 6; i++) // digits generated
        printf("%d", v[i]);
    printf(";\n");
}

void Back() { // generaly form of bactrack function
    natural k = 1, isS, isV;
    Init(k);
    while (k > 0) {
        isS = 0; isV = 0;
        if (k <= 6)
            do {
                isS = Succesor(k);
                if (isS) isV = Valid(k);
            } while (isS && !isV);
            if (isS)
                if (Solution(k))
                    Print();
                else {
                    k++;
                    Init(k);
                }
            else
                k--;
    }
}

int main() {

    Back(); // main call
    system("pause");
    return 0;

}