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

int main(int argc, char* argv[]) {

    int pfd1[2];
    pipe(pfd1);
    int pfd2[2];
    pipe(pfd2);

    int pid1, pid2;

    FILE* out = fdopen(pfd2[1], "w");
    fprintf(out, "%d", 1);
    fflush(out);
    fclose(out);

    int n = strtol(argv[1], NULL, 10);

    if(!(pid1 = fork())) {
        close(pfd1[0]); close(pfd2[1]);

        FILE* in = fdopen(pfd2[0], "r");
        FILE* out = fdopen(pfd1[1], "w");

        int y;
        while(fscanf(in, "%d", &y) > 0) {
            if(y >= n)  {
                break;
            }
            printf("%d %d\n", y, 1);
            fflush(stdout);
            y++;
            fprintf(out, "%d", y);
            fflush(out);

        }

        close(pfd1[1]);
        close(pfd2[0]);
        fclose(in); fclose(out);
        _exit(0);

    }

    if(!(pid2 = fork())) {
        close(pfd2[0]); close(pfd1[1]);

        FILE* in = fdopen(pfd1[0], "r");
        FILE* out = fdopen(pfd2[1], "w");

        int y;
        while(fscanf(in, "%d", &y) > 0) {
            if(y >= n) {
                break;
            }
            printf("%d %d\n", y, 2);
            fflush(stdout);
            y++;
            fprintf(out, "%d", y);
            fflush(out);
        }

        close(pfd2[1]);
        close(pfd1[0]);
        fclose(in); fclose(out);
        _exit(0);
    }

    close(pfd1[0]); close(pfd1[1]);
    close(pfd2[0]); close(pfd2[1]);
    wait(0); wait(0);
    printf("Done\n");
    return 0;
}