#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
int dp[70070][12][12], a[70070], on[70070];
int main(){
cin.tie(NULL);
ios_base::sync_with_stdio(false);
int n, pt = 1, cnt = 0;
string s;
cin >> n >> s;
for (int i=0;i<n;i++){
if (s[i]!='e') {a[pt++] = s[i] - 'a' + 1; continue;}
while(i<n && s[i]=='e') i++, cnt++;
on[pt] = 1;
a[pt++] = s[i] - 'a' + 1;
}
n = pt - 1;
//for (int i=1;i<=n;i++) printf("%c", a[i]+'a'-1);
//printf("\n");
//for (int i=1;i<=n;i++) printf("%d", on[i]);
//printf("\n");
for (int j=1;j<=10;j++){
for (int k=1;k<=10;k++) dp[1][j][k] = 4;
dp[1][j][0] = 2;
dp[1][j][11] = 2;
}
for (int i=2;i<=n;i++){
for (int j=1;j<=10;j++){
for (int k=1;k<=10;k++){
dp[i][j][k] = 1e9;
if (a[i]!=j && a[i]!=k) dp[i][j][k] = min(dp[i][j][k], dp[i-1][j][k] + 1);
if (a[i]!=j) dp[i][j][k] = min(dp[i][j][k], dp[i-1][j][a[i]] + 3);
if (a[i]!=k) dp[i][j][k] = min(dp[i][j][k], dp[i-1][a[i]][k] + 3);
dp[i][j][k] = min(dp[i][j][k], dp[i-1][a[i]][a[i]] + 5);
if (a[i]!=j) dp[i][j][k] = min(dp[i][j][k], dp[i-1][j][0] + 2);
dp[i][j][k] = min(dp[i][j][k], dp[i-1][a[i]][0] + 4);
}
}
for (int j=1;j<=10;j++){
dp[i][j][0] = 1e9;
if (a[i]!=j && !on[i]) dp[i][j][0] = min(dp[i][j][0], dp[i-1][j][0]);
dp[i][j][0] = min(dp[i][j][0], dp[i-1][a[i]][0] + 2);
if (a[i]!=j) dp[i][j][0] = min(dp[i][j][0], dp[i-1][a[i]][j] + 1);
dp[i][j][0] = min(dp[i][j][0], dp[i-1][a[i]][a[i]] + 3);
dp[i][j][11] = 1e9;
if (a[i]!=j) dp[i][j][11] = min(dp[i][j][11], dp[i-1][j][11] + 1);
dp[i][j][11] = min(dp[i][j][11], dp[i-1][a[i]][11] + 3);
if (a[i]!=j) dp[i][j][11] = min(dp[i][j][11], dp[i-1][j][0]);
dp[i][j][11] = min(dp[i][j][11], dp[i-1][a[i]][0] + 2);
}
dp[i][11][0] = 1e9;
if (!on[i]) dp[i][11][0] = min(dp[i][11][0], dp[i-1][11][0]);
dp[i][11][0] = min(dp[i][11][0], dp[i-1][a[i]][0]);
dp[i][11][0] = min(dp[i][11][0], dp[i-1][a[i]][11] + 1);
dp[i][11][0] = min(dp[i][11][0], dp[i-1][a[i]][a[i]] + 2);
}
//printf("%d\n", dp[1][4][0]);
printf("%d\n", dp[n][11][0] + cnt*2);
return 0;
}
