// coached by rainboy
#include <algorithm>
#include <iostream>
using namespace std;
const int N = 70000;
const int A = 10;
const int INF = 0x3f3f3f3f;
char aa[N + 1];
bool ee[N + 1];
int dp[A][A + 1], dq[A][A + 1];
int main() {
ios_base::sync_with_stdio(false), cin.tie(NULL);
int n; cin >> n >> aa;
int k = 0, m = 0; bool e = false;
for (int i = 0; i < n; i++)
if (aa[i] == 'e')
k += 2, e = true;
else
aa[m] = aa[i] - 'a' - (aa[i] > 'e'), ee[m] = e, m++, e = false;
n = m;
for (int a = 0; a < A; a++) {
for (int b = 0; b <= A; b++)
dp[a][b] = INF;
dp[a][A] = 2;
}
for (int i = 1; i < n; i++) {
for (int a = 0; a < A; a++)
for (int b = 0; b <= A; b++)
dq[a][b] = INF;
for (int a = 0; a < A; a++)
for (int b = 0; b <= A; b++) {
int x = dp[a][b];
if (x == INF)
continue;
if (b == A) {
if (a == aa[i])
for (int c = 0; c < A; c++)
dq[c][A] = min(dq[c][A], x + 2);
else if (!ee[i])
dq[a][A] = min(dq[a][A], x);
else
for (int c = 0; c < A; c++)
dq[c][a] = min(dq[c][a], x + 2);
} else {
x++;
if (a == aa[i]) {
for (int c = 0; c < A; c++)
if (b == aa[i])
for (int d = 0; d <= A; d++)
dq[c][d] = min(dq[c][d], x + 2 + (d < A ? 2 : 0));
else
dq[c][b] = min(dq[c][b], x + 2);
} else {
if (b == aa[i])
for (int d = 0; d <= A; d++)
dq[a][d] = min(dq[a][d], x + (d < A ? 2 : 0));
else
dq[a][b] = min(dq[a][b], x);
}
}
}
for (int a = 0; a < A; a++)
for (int b = 0; b <= A; b++)
dp[a][b] = dq[a][b];
}
cout << k + dp[A - 1][A] - 2 << '\n';
return 0;
}
