#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>

void
work(int snum, FILE *in, FILE *out, int max)
{
    int a;
    while (fscanf(in, "%d", &a) == 1) {
        printf("%d %d\n", snum, a);
        fflush(stdout);
        a++;
        if (a > max)
            exit(0);
        fprintf(out, "%d ", a);
        fflush(out);
    }
    exit(0);
}

int main(int argc, char *argv[])
{
    int max = atoi(argv[1]);

    int p12[2];
    int p21[2];

    pipe(p12);
    pipe(p21);

    if (!fork()) {
        close(p21[1]);
        close(p12[0]);
        FILE *in1 = fdopen(p21[0], "r");
        FILE *out1 = fdopen(p12[1], "w");
        work(1, in1, out1, max);
    }
    if (!fork()) {
        close(p12[1]);
        close(p21[0]);
        FILE *in2 = fdopen(p12[0], "r");
        FILE *out2 = fdopen(p21[1], "w");
        work(2, in2, out2, max);
    }
    int x = 1;
    FILE *out = fdopen(p21[1], "w");
    fprintf(out, "%d ", x);
    fflush(out);

    close(p12[0]);
    close(p12[1]);
    close(p21[0]);
    close(p21[1]);
    wait(NULL);
    wait(NULL);
    printf("Done\n");
    return 0;
}