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#include<iostream>

using namespace std;
int tab[201719];
int main(){
    int n, rek = 0;
    cin>>n;
    for (int i = 0; i<n; i++){
        int a;
        cin>>a;
        tab[a]++;
        if (rek < a) rek=a;
    }
    for (int i = 0; i<=rek; i++){
        tab[i+1]+=tab[i]/2;
        if(tab[rek+1]!=0) rek++;
    }
    cout<<rek;
    return 0;
}