轻轻又松松，19行

#include <bits/stdc++.h>
using namespace std;
map<int,int> mp;
int main(){
	int n,x,ans = 0;
	scanf("%d",&n);
	for(int i = 1;i<=n;i++){
		scanf("%d",&x);
		mp[x]++;
	}
	for(int j = 0;j<=x;j++){
		if(mp[j]/2 && j == x)x++;
		mp[j+1]+=mp[j]/2;
		mp[j] = mp[j]%2;
		if(!mp[j])ans++;
	}
	printf("%d",ans);
	return 0;
}