P11227

#include <iostream>
#include <map>
#define int long long
using namespace std;
int n,ans;
string s;
map <char,int> a;
map <char,int> b;
signed main(){
	cin>>n;
	for(int i=1;i<=n;++i){
		cin>>s;
		if(a[s[0]]==1&&b[s[1]]==1) continue;
		a[s[0]]=1;
		b[s[1]]=1;
		ans++;
	}
	cout<<52-ans;
	return 0;
}