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#include <cstdio>
using namespace std;

bool A[300005];

int main() {
    for ( int i=0; i<300000; i++ ) A[i]=0;
    int n;
    scanf("%d", &n);
    while ( n-- ) {
        int a;
        scanf("%d",&a);
        while ( A[a] ) {A[a]=0; a++;}
        A[a]=1;
    }
    int a = 250000;
    while (a--) {
        if (A[a]) {
            printf("%d\n",a);
            return 0;
        }
    }

    return 0;
}