#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char* argv[]) {
    short port_num = strtol(argv[1], NULL, 10);
    int sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock == -1) {
        perror("socket");
        abort();
    }

    struct sockaddr_in addr = {
        .sin_family = AF_INET,
        .sin_addr = inet_addr("127.0.0.1"),
        .sin_port = htons(port_num)
    };

    int send_num, recv_num;
    while (scanf("%d", &send_num) > 0) {
        sendto(sock,
               &send_num, sizeof(send_num),
               0,
               (const struct sockaddr*) &addr,
               sizeof(addr));
        recvfrom(sock,
                 &recv_num, sizeof(recv_num),
                 0, NULL, NULL);
        printf("%d\n", recv_num);
    }

    close(sock);
}