다음 C 프로그램의 실행 결과를 쓰시오.

#include <stdio.h>

struct Node {
    int value;
    struct Node *next;
};

void swap_pairs(struct Node *node) {
    while (node != NULL && node->next != NULL) {
        int temp = node->value;
        node->value = node->next->value;
        node->next->value = temp;
        node = node->next->next;
    }
}

int main(void) {
    struct Node n1 = {1, NULL};
    struct Node n2 = {2, NULL};
    struct Node n3 = {3, NULL};
    n1.next = &n3;
    n3.next = &n2;

    swap_pairs(&n1);
    for (struct Node *p = &n1; p != NULL; p = p->next) {
        printf("%d", p->value);
    }
    return 0;
}