#include <bits/stdc++.h>
#define _ ios_base::sync_with_stdio(false);cin.tie(0);
using namespace std;
#define pb push_back
#define pob pop_back
#define pf push_front
#define pof pop_front
#define mp make_pair
#define all(a) a.begin(),a.end()
#define bitcnt(x) __builtin_popcountll(x)
#define MOD 1000000007
#define total 5000005
#define Me 1000000000001
#define NIL 0
#define MAXN 210005
#define EPS 1e-5
#define INF (1<<28)
#define pi 3.141593
typedef unsigned long long int uint64;
typedef long long int ll;
vector<vector<int> > graph;
queue<int> q;
priority_queue <long ,vector<long >,greater<long > > p;//stores min val at top
priority_queue <long ,vector<long > > g;//max_heap
priority_queue< pair< int, string > , vector< pair< int, string> >, greater< pair< int, string > > > pq;// pair inside pq
//make_heap(v.begin(),v.end())-> makes the vector v as max_haep
int main(){
	ios_base::sync_with_stdio(false);
        cin.tie(0);
        cout.tie(0);
         vector<ll>::iterator it;
         //sort(vect.begin(), vect.end(), sortbysec);
         int n,i,x,y=0,l=0,u=0,d=0,sc=0;
         string s;
         char c;
         cin>>n;
         cin>>s;
         x=n-6;
         for(i=0;i<n;i++)
          {
          	c=s[i];
          	if(isupper(c))u++;
          	else if(islower(c))l++;
          	else if(isdigit(c))d++;
          	else sc++;
		  }
		/*cout<<"x="<<x<<endl;
		  cout<<"l="<<l<<endl;
		   cout<<"u="<<u<<endl;
		    cout<<"d="<<d<<endl;
		     cout<<"sc="<<sc<<endl;*/
		  if(l==0)y++;
		  if(u==0)y++;
		  if(d==0)y++;
		  if(sc==0)y++;
		  //cout<<"y="<<y<<endl;
		  if(x<0)
		  {   x=abs(x);
		  	  if(y<=x)
		  	  cout<<x;
		  	  else
		  	  cout<<y;
		  }
		  else
		    cout<<y;
		return 0;
    }