#include<stdio.h>

int main () {
    int N;
    scanf("%d", &N);
    
    if (N < 1) {
        printf("Invalid input\n");
        return 0;
    }
    int ids[N];
    int freq[2001] = {0};
    
    for(int i = 0; i<N; i++) {
        scanf("%d",&ids[i]);
        freq[ids[i] + 1000]++;
    }
    int found = 0;
    for (int i=0 i<N; i++) {
        if (freq[ids[i] + 1000] >1) {
            printf("%d", ids[i]);
            freq[ids[i] + 1000] = 0;
            found = 1;
        }
    }
    if (!found) {
        printf("No duplicates found")
    }
    printf("\n");
    return 0;
}