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#include <bits/stdc++.h>
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#define endl '\n'
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using namespace std;
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typedef long long ll;
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bool solve(){
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    ll n;
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    cin>>n;
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    string str;
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    cin>>str;
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    sort(str.begin(),str.end());
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    priority_queue<ll,vector<ll>,greater<>> pq;
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    ll num=1;
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    for(ll i=1;i<=str.size();i++){
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        if(str[i-1]!=str[i]){
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            pq.push(num);
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            num=1;
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        }else num++;
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    }
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    ll ans=1;
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    if(pq.size()==1)ans=str.size();
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    while(pq.size()>1){
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        ll a=pq.top();pq.pop();
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        ll b=pq.top();pq.pop();
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        ans+=a+b;
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        pq.push(a+b);
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    }
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    if(ans<=n)return true;
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    else return false;
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}
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int main(){
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    ll t;
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    cin>>t;
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    while(t--){
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        if(solve())cout<<"yes"<<endl;
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        else cout<<"no"<<endl;
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    }
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    return 0;
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}