#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
#define FOR(i,a,b) for(int i = (a) , _b = (b); i <= _b; ++i)
#define BIT(mask , x) (((mask) >> (x)) & (1))
#define MASK(x) ((LL)(1) << (x))
#define sz(x) (int)(x).size()
#define Time cerr << "\n Time lapsed : " << 1.0 * clock() / CLOCKS_PER_SEC << " s\n";
template<class T1 , class T2>
bool maximize(T1 &a , T2 b){
if (a < b) return a = b , true; else return false;
}
template<class T1 , class T2>
bool minimize(T1 &a , T2 b){
if (a > b) return a = b , true; else return false;
}
template<class T>
void compress(vector<T>&data){
sort(data.begin() , data.end());
data.resize(unique(data.begin() , data.end()) - data.begin());
}
template<class T1 , class T2>
T2 Find(const vector<T1>&data , T2 y){
return upper_bound(data.begin() , data.end() , y) - data.begin();
}
const int N = (int) 7e4;
const int MAXK = 10;
int n , answer = 0;
bool flag = false;
string s;
vector<int>v;
bool must[N + 2] = {};
int f[N + 2][MAXK + 2];
int g[N + 2][MAXK + 2][MAXK + 2];
int main(){
ios::sync_with_stdio(false);
cin.tie(0) ; cout.tie(0) ;
#define name "main"
if (fopen(name".inp","r")){
freopen(name".inp","r",stdin);
freopen(name".out","w",stdout);
}
cin >> n;
cin >> s; s = '#' + s;
v.push_back(0);
for(int i = 1; i <= n; ++i) {
if (s[i] == 'e'){
answer += 2;
flag = true;
} else{
int c = (int)s[i] - 'a' - (s[i] < 'e' ? 0 : 1);
v.push_back(c);
must[sz(v) - 1] = flag;
flag = false;
}
}
// for(auto& x : v) cout << x << ' '; cout << '\n';
memset(f , 0x3f , sizeof f);
memset(g , 0x3f ,sizeof g);
f[0][v[1]] = 0;
for(int i = 1; i < sz(v); ++i){
for(int c = 0; c < MAXK; ++c){
if (must[i] == false && v[i] != c) minimize(f[i][c] , f[i - 1][c]);
minimize(f[i][c] , f[i - 1][v[i]] + 2);
if (v[i] != c) minimize(f[i][c] , g[i - 1][v[i]][c]);
minimize(f[i][c] , g[i - 1][v[i]][v[i]] + 2);
for(int nxt_c = 0; nxt_c < MAXK; ++nxt_c){
minimize(g[i][c][nxt_c] , f[i - 1][v[i]] + 5);
minimize(g[i][c][nxt_c] , g[i - 1][v[i]][v[i]] + 5);
if (c != v[i]) minimize(g[i][c][nxt_c] , f[i - 1][c] + 3);
if (v[i] != c && v[i] != nxt_c) {
minimize(g[i][c][nxt_c] , g[i - 1][c][nxt_c] + 1);
}
if (v[i] != nxt_c) minimize(g[i][c][nxt_c] , g[i - 1][v[i]][nxt_c] + 3);
if (v[i] != c) minimize(g[i][c][nxt_c] , g[i - 1][c][v[i]] + 3);
}
}
}
cout << f[sz(v) - 1][MAXK - 1] + answer - 2;
return 0;
}
