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#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAXP 201720

int main() {
        int n, a;
        char s[MAXP];

        bzero(s, MAXP);
        scanf("%d", &n);
        while (n--) {
                scanf("%d", &a);
                s[a]++;
                while(s[a] > 1) { s[a] = 0; s[++a]++; }
        }
        a = MAXP;
        while (!s[--a]);
        printf("%d\n", a);

        return 0;
}