#include<bits/stdc++.h>
using namespace std;
int n,ans=1e9;
string s;
int cnt,v[505],vis[505];
void dfs(string x,int f,int d,int sum){
    if(d==cnt){
        ans=min(sum,ans);
        return;
    }
    for(int i=1;i<=cnt;i++){
        if(vis[v[i]])
            continue;
        if(v[i]>f){
            vis[v[i]]=1;
            dfs(x,v[i]+1,d+1,sum+3);
        }
        else{
            int tot=0;
            for(int j=v[i];j<=f;j++){
                if(!vis[j])tot++;
            }vis[v[i]]=1;
            dfs(x,v[i]+1,d+1,sum+tot);
        }
        vis[v[i]]=0;
    }
}
int main(){
    freopen("become.in","r",stdin);
    freopen("become.out","w",stdout);
    cin>>n>>s;
    for(int i=0;i<n;i++){
        if(s[i]=='e'){
            v[++cnt]=i;
        }
    }
    dfs(s,0,0,0);
    cout<<ans+cnt;
    return 0;
}