// 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)
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int maxn = 70010, mod = 1e9 + 7, inf = 1e9 + 10;
int nxt[maxn][10], lst[10];
struct Hash{
int operator() (const pii &p)const{
return hash<ll>()( 1ll * p.F * maxn + p.S );
}
};
unordered_map<pii, int, Hash> dp;
vector<int> poses;
int solve(int i, int j){
if(i >= sz(poses))
return 0;
if(dp.count({i, j}))
return dp[{i, j}];
int ans = inf;
if(j >= poses[i])
ans = j - poses[i] + solve( upper_bound(poses.begin(), poses.end(), j) - poses.begin(), poses[i] );
if(nxt[ poses[i] ][8] + 10 < j)
return dp[{i, j}] = ans;
int pt = lower_bound(nxt[j], nxt[j] + 10, poses[i]) - nxt[j];
for(int w = 8 ; w >= 0 && nxt[j][w] != j && w >= pt-1; w--)
ans = min(ans, 2 + solve(i, nxt[j][w]));
return dp[{i, j}] = ans;
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie();
dp.reserve(1<<17);
dp.max_load_factor(0.25);
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]);
sort(nxt[i], nxt[i] + 9);
nxt[i][9] = inf;
int id = (s[i] - 'a') - (s[i] > 'e');
lst[id] = i;
}
ans+= solve(0, 0);
return cout << ans << "\n", 0;
}
