#include <bits/stdc++.h>
#define pb push_back
#define fi first
#define se second
#define Mup(a,x) a=max(a, x)
#define mup(a,x) a=min(a, x)
#define all(v) v.begin(),v.end()
#define lb lower_bound
#define INF (1ll<<60)
#define MOD 1'000'000'007
using namespace std;
typedef long long LL;
typedef pair<int,int> pii;
int M, N, X, sum, ans=MOD;
int A[70707], D[70707][11][11];
bool E[70707];
int main(){
char c;
bool tf = false;
scanf("%d", &M);
for (int i=0; i<M; i++){
scanf(" %c", &c);
if (c != 'e'){
A[++N] = c-'a'+1+(c<'e'?1:0);
if (tf) X = N;
E[N] = tf, tf = false;
}
else tf = true, sum += 2;
}
if (!X){puts("0"); return 0;}
memset(D, 1, sizeof D);
for (int i=2; i<=10; i++) D[1][i][0] = 2;
for (int i=1; i<N; i++){
for (int j=2; j<=10; j++){
if (A[i+1] == j){
if (i+1>=X) ans = min(ans, min(D[i][j][0], D[i][j][1]));
for (int k=2; k<=10; k++){
D[i+1][k][0] = min(D[i+1][k][0], D[i][j][0]+2);
D[i+1][k][1] = min(D[i+1][k][1], D[i][j][1]+3);
}
}
else{
if (!E[i+1]) D[i+1][j][0] = min(D[i+1][j][0], D[i][j][0]);
D[i+1][j][1] = min(D[i+1][j][1], min(D[i][j][0], D[i][j][1])+1);
for (int k=2; k<=10; k++) D[i+1][j][k] = min(D[i+1][j][k], D[i][j][0]+3);
}
for (int k=2; k<=10; k++){
if (A[i+1] == j){
if (j == k) for (int l=2; l<=10; l++) D[i+1][l][0] = min(D[i+1][l][0], D[i][j][k]+2);
else{
for (int l=2; l<=10; l++) D[i+1][l][k] = min(D[i+1][l][k], D[i][j][k]+3);
D[i+1][k][0] = min(D[i+1][k][0], D[i][j][k]);
}
}
else if (A[i+1] != k) D[i+1][j][k] = min(D[i+1][j][k], D[i][j][k]+1);
}
}
}
printf("%d\n", ans+sum);
return 0;
}
