#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template <typename T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define vt vector
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef vector<int> vi;
template<class T> bool chmin(T& a, const T& b) {
return b<a?a=b, 1:0;
}
template<class T> bool chmax(T& a, const T& b) {
return a<b?a=b, 1:0;
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());
int k(int a, int b) {
if(a==b)return 1e9;
return 0;
}
int u(int v) {
if(v)return 1e9;
return 0;
}
int main() {
cin.tie(0)->sync_with_stdio(0);
cin.exceptions(cin.failbit);
int n;
string s;
cin >> n >> s;
int ans=0;
reverse(all(s));
while(sz(s) and s.back() == 'e') {
ans++;
s.pop_back();
}
reverse(all(s));
vt<bool> need(n);
{
string tmp = "";
for(int i = 0;i<n;i++) {
if(s[i] == 'e') {
ans+=2;
continue;
}
if(i == 0 or s[i-1] == 'e') {
need[tmp.size()]=1;
}
tmp.push_back(s[i]);
tmp.back()-='a';
}
swap(tmp, s);
}
n=s.size();
vt dp2(n+1, vt(12, vt(12, 0)));
vt dp1(n+1, vt(12, (int)1e9));
for(int i = 0;i<12;i++) {
if(s[i] != i)dp1[0][i] = 2;
}
for(int i = 0;i<n;i++) {
for(int j = 0;j<12;j++) {
dp1[i+1][j] = min({dp1[i][j] + k(s[i], j) + u(need[i]), dp1[i][s[i]] + 2, dp2[i][s[i]][j]+k(s[i], j), dp2[i][s[i]][s[i]]+2});
for(int l = 0;l<12;l++) {
dp2[i+1][j][l] = min({dp1[i][j] + 3 + k(j, s[i]), dp1[i][s[i]] + 5, dp2[i][j][l]+1 + k(j, s[i]) + k(l, s[i]), dp2[i][s[i]][s[i]]+5});
}
}
}
ans+=dp1[n][11];
cout << ans << "\n";
}
