// And you curse yourself for things you never done
#include<bits/stdc++.h>
#define F first
#define S second
#define PB push_back
#define sz(s) int((s).size())
#define bit(n,k) (((n)>>(k))&1)
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int maxn = 70100, mod = 1e9 + 7, inf = 1e9 + 10;
int nxt[maxn][10], nxt2[maxn][10], lst[10], a[maxn];
int dp[maxn][10], DP[maxn], DP2[maxn], DP3[maxn];
vector<int> poses;
int dis(int a, int b){
if(a > b)
return inf;
if(a == b)
return 0;
int mx = a;
for(int i = 0; i < 9; i++){
if(nxt[a][i] <= b)
mx = max(mx, nxt[a][i]);
}
return 2 + dis(mx, b);
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie();
int n;
cin >> n;
string _s, s;
cin >> _s;
int ans = 0;
for(int i = 0; i < n; i++){
if(_s[i] == 'e')
ans+= 2;
if(_s[i] == 'e' && _s[i + 1] != 'e')
poses.PB(sz(s));
if(_s[i] != 'e')
s+= _s[i];
}
memset(lst, -1, sizeof lst);
memset(nxt, -1, sizeof nxt);
n = sz(s);
for(int i = n-1; i >= 0; i--){
for(int j = 0; j < 9; j++)
nxt[i][j] = (lst[j] == -1 ? i : lst[j]);
int id = (s[i] - 'a') - (s[i] > 'e');
a[i] = id;
lst[id] = i;
for(int j = 0; j < 9; j++)
nxt2[i][j] = (lst[j] == -1 ? i : lst[j]);
}
for(int i = 0; i < maxn; i++){
for(int j = 0; j < 10; j++)
dp[i][j] = inf;
DP[i] = DP2[i] = DP3[i] = inf;
}
for(int i = poses.back(); i < maxn; i++){
DP[i] = DP2[i] = DP3[i] = 0;
}
int pt = sz(poses) - 1;
for(int i = poses.back() - 1; i >= 0; i--){
for(int j = 0; j < 9; j++){
if(nxt[i][j] > i){
DP3[i] = min(DP3[i], 2 + DP3[ nxt[i][j] ] + nxt[i][j] - i);
}
}
for(int j = 0; j < 9; j++){
if(nxt[i][j] > i){
if(nxt[i][j] < poses[pt]) // <= ?
DP2[i] = min(DP2[i], 2 + DP2[ nxt[i][j] ]);
else
DP2[i] = min(DP2[i], 2 + DP3[ nxt[i][j] ] + nxt[i][j] - poses[pt]);
}
}
DP[i] = DP2[i];
for(int j = 0; j < 9; j++){
int x = nxt[i][j];
if(x == i)
continue;
if(x <= poses[pt]){
DP[i] = min(DP[i], 2 + DP[x]);
}
else{
for(int k = 0; k < 9; k++){
DP[i] = min(DP[i], 2 + x - poses[pt] + dis(poses[pt], nxt2[x][k]) + dp[x][k]);
}
}
}
for(int j = 0; j < 9; j++){
int x = nxt2[i][j];
if(x <= poses[pt]){
dp[i][j] = DP[x];
}
else{
dp[i][j] = x - poses[pt] + DP3[x];
for(int k = 0; k < 9; k++)
dp[i][j] = min(dp[i][j], x - poses[pt] + dis(poses[pt], nxt2[x][k]) + dp[x][k]);
}
for(int k = 0; k < 9; k++){
int xx = nxt[i][k];
if(xx == i)
continue;
for(int k2 = 0; k2 < 9; k2++)
dp[i][j] = min(dp[i][j], 2 + xx - i + dis(x, nxt2[xx][k2]) + dp[xx][k2]);
}
}
if(pt > 0 && poses[pt-1] == i){
pt--;
}
}
ans+= DP[0];
return cout << ans << "\n", 0;
}
