#include <bits/stdc++.h>
#define FOR(i, x, y) for (int i = x; i < y; i++)
typedef long long ll;
using namespace std;
bool underlined[70000];
int t[70000], p[70000][10], q[70000][10][10];
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, t_cnt = 0, e_cnt = 0;
string s;
cin >> n >> s;
underlined[0] = true;
t[t_cnt++] = s[0] - 'a' - (s[0] > 'e');
FOR(i, 1, n) {
if (s[i] != 'e') {
if (s[i - 1] == 'e') underlined[t_cnt] = true;
t[t_cnt++] = s[i] - 'a' - (s[i] > 'e');
} else e_cnt++;
}
memset(q[0], 0x3f, sizeof q[0]);
FOR(c, 0, 10) p[0][c] = (c == t[0] ? 0 : 2);
FOR(i, 0, t_cnt) {
FOR(c, 0, 10) {
p[i + 1][c] = min(p[i][t[i]], q[i][t[i]][t[i]]) + 2;
if (c != t[i]) {
p[i + 1][c] = min(p[i + 1][c], q[i][t[i]][c]);
if (!underlined[i]) p[i + 1][c] = min(p[i + 1][c], p[i][c]);
}
FOR(d, 0, 10) {
q[i + 1][c][d] = min(p[i][t[i]], q[i][t[i]][t[i]]) + 5;
if (c != t[i]) {
q[i + 1][c][d] = min(q[i + 1][c][d], min(p[i][c], q[i][c][t[i]]) + 3);
if (d != t[i]) q[i + 1][c][d] = min(q[i + 1][c][d], q[i][c][d] + 1);
}
if (d != t[i]) q[i + 1][c][d] = min(q[i + 1][c][d], q[i][t[i]][d] + 3);
}
}
}
cout << 2 * e_cnt + p[t_cnt][9] - 2;
return 0;
}
