#include <iostream>
#include <vector>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>

using namespace std;
void dfs(vector<vector<char>>&graph,int cur,unordered_set<char> &set,int depth,int index,int &maxV){
    if(cur<0||cur>=graph.size())return;
    if(index<0||graph[cur].size()<=index)return;
  
    if(set.count(graph[cur][index])){//set已存在该项，说明已成环，退出DFS
        return;
    }
    set.emplace(graph[cur][index]);   
    maxV=max(depth+1,maxV);
    for(int i=index+1;i<graph[cur].size();i++){
        int num=graph[cur][i];
        for(int j=0;j<graph[num].size();j++){
            dfs(graph,num,set,depth+1,j,maxV);
        }
    }
}
int calRes(vector<pair<char,char>>&cards){
    int maxV=0;
    int n=cards.size();
    vector<vector<char>>graph;
    for(int i=0;i<n;i++){
        vector<char>tmp;
        for(int j=0;j<n;j++){
            if(i==j)continue;
            if((cards[i].first==cards[j].first)||(cards[i].second==cards[j].second)){
                tmp.push_back(j);
            }
        }
        graph.push_back(tmp);
        //for(auto ii:tmp)cout<<(int)ii<<" ";
        //cout<<"EDN"<<endl;
    }//将牌和颜色的打出规则构建成图
    unordered_set<char> set;
    for(int i=0;i<n;i++){
        dfs(graph,i,set,1,0,maxV);
        set.clear();
    }//暴力DFS遍历
    return maxV;
}


int main(){
    vector<char>numV,colorV;
    vector<pair<char, char>>cards;
    char tmp;
    while(cin>>tmp){
        if(tmp>='1'&&tmp<='9'){
            numV.push_back(tmp);
        }else{
            colorV.push_back(tmp);
        }
    }   
    for(auto i=0;i<numV.size();i++){
        cards.push_back({numV[i],colorV[i]});
    }
    cout<<calRes(cards)<<endl; 
    return 0;
}