// Born_To_Laugh - Hughie Do
#include <bits/stdc++.h>
#define alle(AC) AC.begin(), AC.end()
#define fi first
#define se second
using namespace std;
typedef long long ll;
[[maybe_unused]] const ll MOD = 998244353, INF = 1e9 + 7;
const int maxn = 7e4 + 10;
string s;
int n;
int a[maxn];
vector<int> jum[maxn];
map<pair<int,int>, int> mp;
int laste = INF;
int cnte = 0;
int nxtem[maxn];
void solve(){
cin >> n >> s;
s = "%" + s;
vector<int> last(11, INF);
for(int i=n; i>=1; --i){
jum[i] = last;
last[s[i] - 'a'] = i;
if(s[i] == 'e'){
if(laste == INF)laste = i;
cnte++;
nxtem[i] = nxtem[i + 1];
}
else nxtem[i] = i;
}
if(cnte == 0){
cout << 0 << '\n';
return;
}
int ans = INF;
mp[{1, 1}] = 0;
while(!mp.empty()){
auto x = *mp.begin();
mp.erase(mp.begin());
if(x.fi.se >= laste){
ans = min(ans, x.se);
}
// cout << x.fi.fi << ' ' << x.fi.se << " : " << x.se << '\n';
for(int i=0; i<=10; ++i){
if(i == 'e' - 'a')continue;
if(jum[x.fi.fi][i] == INF)continue;
int j = jum[x.fi.fi][i];
int nxte = jum[x.fi.se]['e' - 'a'];
if(j >= nxte){
if(mp[{nxtem[nxte], j}] == 0)mp[{nxtem[nxte], j}] = INF;
mp[{nxtem[nxte], j}] = min(mp[{nxtem[nxte], j}], x.se + 2 + j - nxte);
}
else{
if(mp[{j, j}] == 0)mp[{j, j}] = INF;
mp[{j, j}] = min(mp[{j, j}], x.se + 2);
}
}
}
cout << ans + cnte << '\n';
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
solve();
}
