#include <bits/stdc++.h>
using namespace std;
using lint = long long;
using pi = pair<int, int>;
const int MAXN = 70005;
int n;
char str[MAXN], buf[MAXN];
int chk[MAXN];
int dp[MAXN][10];
int d2[MAXN][10][10];
int f(int v, int w);
int g(int v, int win, int wout);
int g(int v, int win, int wout){
if(v == n - 1) return 1e9;
if(~d2[v][win][wout]) return d2[v][win][wout];
int ret = 1e9;
if(win + 'a' == str[v + 1] && wout + 'a' == str[v + 1]){
for(int i=0; i<10; i++){
ret = min(ret, f(v + 1, i) + 3);
}
for(int i=0; i<10; i++){
for(int j=0; j<10; j++){
ret = min(ret, g(v + 1, i, j) + 5);
}
}
}
else if(win + 'a' == str[v + 1]){
for(int i=0; i<10; i++){
ret = min(ret, g(v + 1, i, wout) + 3);
}
ret = min(ret, f(v + 1, wout) + 1);
}
else if(wout + 'a' == str[v + 1]){
for(int i=0; i<10; i++){
ret = min(ret, g(v + 1, win, i) + 3);
}
}
else{
ret = min(ret, g(v + 1, win, wout) + 1);
}
return d2[v][win][wout] = ret;
}
int f(int v, int w){
if(v == n - 1) return w == 4 ? 0 : 1e9;
if(~dp[v][w]) return dp[v][w];
int ret = 1e9;
if(str[v + 1] == w + 'a'){
for(int i=0; i<10; i++){
ret = min(ret, f(v + 1, i) + 2);
}
return dp[v][w] = ret;
}
for(int i=0; i<10; i++){
ret = min(ret, g(v + 1, w, i) + 2);
}
if(!chk[v + 1]) ret = min(ret, f(v + 1, w));
return dp[v][w] = ret;
}
int main(){
scanf("%d %s",&n,buf);
n = 0;
int ecnt = 0;
for(int i=0; buf[i]; i++){
if(buf[i] == 'e'){
ecnt++;
chk[n] = 1;
}
else str[n++] = buf[i];
}
memset(dp, -1, sizeof(dp));
memset(d2, -1, sizeof(d2));
int ret = 1e9;
for(int i=0; i<10; i++){
ret = min(ret, f(0, i));
}
cout << ret + ecnt * 2 << endl;
}
