#include <cstdio>#include <cstdlib>#include <vector>using namespace std;const int NUM_RANGE = 10001;int tbl[NUM_RANGE];int main() {    int N;    scanf("%d", &N);    vector<int> nums(N);        int i=0;    for (i=0; i<NUM_RANGE; i++) {        tbl[i] = false;    }        for (i=0; i<N; i++) {        scanf("%d", &(nums[i]));        tbl[nums[i]]++;    }        for (i=0; i<N; i++) {        if (1 == tbl[nums[i]]) {            printf("%d\n", nums[i]);            break;        }    }    if (i == N) {        printf("None\n");    }    return 0;}