#include <cstdio>

unsigned long coins[1000000] = {0};

int main(void) {
	unsigned count, exp, max = 0;
	
	scanf("%u",&count);
	
	for(unsigned i=0;i<count;++i) {
		scanf("%u",&exp);
		++coins[exp];
		
		if(exp>max) {
			max = exp;
		}
	}
	
	for(unsigned i=0;i<=max;++i) {
		if(coins[i]>1) {
			coins[i+1] += coins[i]/2;
			
			if(i==max)
				++max;
		}
	}
	
	printf("%u\n",max);
	
	return 0;
}