#include<stdio.h>

int main() { 
    int x, n;
    int A[n];

    scanf("%d %d", &x, &n);
    for (int i = 0; i < n; i++) { 
        scanf("%d", &A[i]);
    } 

    for (int i = 0; i < 6; i++) { 
        int a = x - i;
        int b = x + i;
        for (int j = 0; j < n; j++) { 
            if (a == A[j]) goto loopend;
        } 

        printf("%d", a);

        for (int j = 0; j < n; j++) { 
            if (b == A[j]) goto loopend;
        } 

        printf("%d", b);
        loopend:
 

        continue;
    }

    return 0;         