백준 5597 - C

#include <stdio.h>

#define STUDENT_NUM 30
int main(void) {
    int student[STUDENT_NUM+1] = {0, };
    int num;
    
    for (int i = 0; i < 28; i++) {
        scanf("%d", &num);
        
        student[num] = num;
    }
    
    for (int i = 1; i <= STUDENT_NUM; i++) {
        if (student[i] == 0) printf("%d\n", i);
    }
}