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

#define max(a, b) a>b?a:b

int main() {
    int n, a, m = -1;
    const int LEN = 201718;
    int *tmp = calloc(LEN, sizeof(int));
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%d", &a);
        tmp[a]++;
        m = max(m, a);
    }
    for (int i = 0; i < m; i++) {
        tmp[i + 1] += tmp[i] / 2;
        tmp[i] %= 2;
    }
    printf("%d\n", m + (int) (log(tmp[m]) / log(2)));
    return 0;
}