#include <bits/stdc++.h>
#define int long long
#define umi(x, y) (x = min(x, y))
#define uma(x, y) (x = max(x, y))
using namespace std;
int dp[70004][12][12];
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int n; cin >> n;
string in; cin >> in;
string s;
vector<int> must;
int cnt = 0, ans = 0;
for(auto&i:in){
if(i == 'e') ++cnt;
else{
s += i; must.push_back(!!cnt);
ans += cnt * 2;
cnt = 0;
}
}
while((int)must.size() && !must.back()){
must.pop_back(); s.pop_back();
}
must.push_back(0), s += 'a' + 10;
n = (int)s.size();
for(int i = 0; i < 70004; ++i) for(int j = 0; j < 12; ++j) for(int k = 0; k < 12; ++k) dp[i][j][k] = (int)1e9;
for(int i = 1; i <= 11; ++i) dp[1][i][0] = 0;
for(int i = 1; i < n; ++i){
for(int j = 1; j <= 11; ++j){
for(int k = 0; k <= 11; ++k){
if(!k){
if(!must[i]){
umi(dp[i + 1][j][k], dp[i][j][k] + (s[i] - 'a' + 1 == j) * 2);
}
if(s[i] - 'a' + 1 == j){
for(int x = 1; x <= 11; ++x){
umi(dp[i + 1][x][k], dp[i][j][k] + (s[i] - 'a' + 1 == j) * 2);
}
}
for(int x = 1; x <= 11; ++x){
umi(dp[i + 1][j][x], dp[i][j][k] + 1 + (s[i] - 'a' + 1 == j) * 2);
}
}
else{
if(s[i] - 'a' + 1 == j){
umi(dp[i + 1][k][0], dp[i][j][k] + 2 + (s[i] - 'a' + 1 == k) * 2);
for(int x = 1; x <= 11; ++x){
umi(dp[i + 1][x][k], dp[i][j][k] + 3 + (s[i] - 'a' + 1 == k) * 2);
}
}
else if(s[i] - 'a' + 1 == k){
for(int x = 1; x <= 11; ++x){
umi(dp[i + 1][j][x], dp[i][j][k] + 3 + (s[i] - 'a' + 1 == j) * 2);
}
}
else{
umi(dp[i + 1][j][k], dp[i][j][k] + 1 + (s[i] - 'a' + 1 == k) * 2);
}
}
}
}
}
cout << ans + dp[n - 1][s[n - 2] - 'a' + 1][11] - 1;
return 0;
}
