#include <bits/stdc++.h>
using namespace std;
const int N = 70005;
const int INF = 0x3f3f3f3f;
int n;
int cost;
int f1[N][11];
int f2[N][11][11];
bool flag[N];
string s;
void upd(int &x, int y) { x = min(x, y); }
int main() {
ios::sync_with_stdio(false);
cin >> n >> s;
string t = s; s.clear();
for (int i = 0; i < n; ++i) {
if (t[i] == 'e') {
flag[s.size()] = 1, cost += 2;
}
else s.push_back(t[i]);
}
n = s.size();
memset(f1, INF, sizeof f1);
memset(f2, INF, sizeof f2);
int x = s[0] - 'a';
f1[0][x] = f2[0][x][x] = 0;
for (int i = 1; i <= n; ++i) {
int x = s[i - 1] - 'a';
for (int j = 0; j <= 10; ++j) {
if (j != x && !flag[i - 1]) {
upd(f1[i][j], f1[i - 1][j]);
}
upd(f1[i][j], f1[i - 1][x] + 2);
if (x != j) {
upd(f1[i][j], f2[i - 1][x][j]);
}
upd(f1[i][j], f2[i - 1][x][x] + 2);
}
for (int j = 0; j <= 10; ++j) {
for (int k = 0; k <= 10; ++k) {
if (j != x) {
upd(f2[i][j][k], f1[i - 1][j] + 3);
}
upd(f2[i][j][k], f1[i - 1][x] + 5);
if (j != x && k != x) {
upd(f2[i][j][k], f2[i - 1][j][k] + 1);
}
if (j != x) {
upd(f2[i][j][k], f2[i - 1][j][x] + 3);
}
if (k != x) {
upd(f2[i][j][k], f2[i - 1][x][k] + 3);
}
upd(f2[i][j][k], f2[i - 1][x][x] + 5);
}
}
}
cout << f1[n][10] + cost - 2;
}
