#include <unistd.h>

int main() {
    char digit[3];
    digit[0] = '0';

    while(digit[0] <= '9'){
        digit[1] = '0';
        while(digit[1] <= '9'){
            digit[2] = '0';
            while(digit[2] <= '9'){
                write(1, digit, 3);
                write(1, "\n", 1);
                digit[2]++;
            }
            digit[1]++;
        }
        digit[0]++;
    }


    return 0;
}