#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<queue>
#include<iostream>
using namespace std;priority_queue<int, vector<int>, greater<int> >Q;//从小到大，优先队列char str[10001];
int huf[26];
int n;void solve()
{int ans=0;int a,b;while(Q.size()!=1){a=Q.top();//优先队列区最小的数（认为已经排好顺序了）
        Q.pop();b=Q.top();Q.pop();Q.push(a+b);//把新的根入队；ans+=(a+b);//本题要求的权值；
    }printf(ans<=n?"yes\n":"no\n");
}int main()
{int T,i,len;scanf("%d",&T);while(T--){while(!Q.empty())//保证队列为空
            Q.pop();memset(huf,0,sizeof(huf));scanf("%d",&n);scanf("%s",str);len=strlen(str);for(i=0;i<len;i++){huf[str[i]-'a']++;//统计各个字母的个数
        }for(i=0;i<26;i++)if(huf[i])//如果有字母就入队
                Q.push(huf[i]);if(Q.size()==1)//没有子叶的情况
        {int m=Q.top();Q.pop();printf(m<=n?"yes\n":"no\n");}elsesolve();}return 0;
}

#include<iostream>
#include<cstring>
#include<cstdlib>
using namespace std;
struct node
{int weight;int parent,left,right;
};
char a[100001];
int huf(int str[],int size)
{int i,lenth=2*size,min1,min2,x,y,sum=0,j;struct node *hf;hf=(struct node *)malloc(lenth*sizeof(struct node));//开创for(i=size;i<lenth;i++){hf[i].weight=str[i-size];hf[i].parent=hf[i].left=hf[i].right=0;}for(i=size-1;i>0;i--){min1=min2=10000000;x=y=0;for(j=i+1;j<lenth;j++){if(min1>hf[j].weight&&hf[j].parent==0){min2=min1;y=x;min1=hf[j].weight;x=j;}else if(min2>hf[j].weight&&hf[j].parent==0){y=j;min2=hf[j].weight;}}hf[i].weight=min1+min2;sum=sum+hf[i].weight;hf[i].parent=0;if(x>y)swap(x,y);hf[i].left=y;hf[i].right=x;hf[x].parent=i;hf[y].parent=i;}return sum;
}
int main()
{int T,n,i,j,len,num[26],b[26];while(scanf("%d",&T)!=EOF){while(T--){len=0;memset(b,0,sizeof(b));scanf("%d",&n);getchar();scanf("%s",a);for(i=0;a[i]!='\0';i++)b[a[i]-'a']++;//把字母个数存入数组for(i=0;i<26;i++)if(b[i]!=0)num[len++]=b[i];//除去空字母if(len==1){if(num[0]<=n)printf("yes\n");elseprintf("no\n");} else{if(huf(num,len)<=n)printf("yes\n");elseprintf("no\n");}}}return 0;
}