#include <iostream>
#include <math.h>
#include <numeric>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <queue>
#include <queue>
#include <stack> 
#include <sstream>
#include <set>

typedef  long long ll;
const int dx[8]={1,0,-1,0,1,-1,-1,1};
const int dy[8]={0,1,0,-1,1,1,-1,-1};
const int dr[4] = {-1, 0, 1, 0};
const int dc[4] = { 0, 1, 0,-1};
const int INF = 1e9;
#define FOR(i, a, n) for(int i = (int)(a); i < (int)(n); ++i)
#define REP(i, n) FOR(i, 0, n)
#define SORT(a) sort(a.begin(),a.end())
#define REVERSE(a) reverse(a.begin(),a.end())
int guki (int a){
    if(a%2==0) return 0;
    else return 1;
}
int gcd(int a, int b){
    if(a%b==0){
        return b;
    }else{
        return (gcd(b,a%b));
    }
}
int lcm(int a, int b){
    int x = gcd(a,b);
    return (a*b/x);
}

using namespace std;
// now

struct UnionFind {
    vector<int> d;
    UnionFind(int n=0) : d(n,-1){}
    int Find (int x){//根の番号を探す
        if(d[x] < 0) return x;
        return d[x] = Find(d[x]);
    }
    bool unite (int x, int y){
        x = Find(x); y = Find(y);
        if(x == y ) return false;
        if(d[x] < d[y]){
            swap(x,y);
        }
        d[x] += d[y];
        d[y] = x;
        return true;
    } 

    bool same(int x, int y){
        return Find(x) == Find(y);
    }
    int size(int x) {
        return (-d[Find(x)]);
    }
};


ll nCr (ll n, ll r){
    ll ans = 1;
    for(ll i = n ; i > n-r ; i --){
        ans *= i;
    }
    for(ll i = 1 ; i<= r; i ++){
        ans /= i;
    }
    return ans ;
}

int nPr (int n,int r){
    int ans = 1;
    for(int i = n ; i > n-r ; i --){
        ans *= i;
    }
    return ans ;
}
// auto mod int
// https://youtu.be/L8grWxBlIZ4?t=9858
// https://youtu.be/ERZuLAxZffQ?t=4807 : optimize
// https://youtu.be/8uowVvQ_-Mo?t=1329 : division
const int mod = 1000000007;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x=0):x((x%mod+mod)%mod){}
  mint operator-() const { return mint(-x);}
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod-a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) { (x *= a.x) %= mod; return *this;}
  mint operator+(const mint a) const { return mint(*this) += a;}
  mint operator-(const mint a) const { return mint(*this) -= a;}
  mint operator*(const mint a) const { return mint(*this) *= a;}
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t>>1);
    a *= a;
    if (t&1) a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod-2);}
  mint& operator/=(const mint a) { return *this *= a.inv();}
  mint operator/(const mint a) const { return mint(*this) /= a;}
};
istream& operator>>(istream& is, mint& a) { return is >> a.x;}
ostream& operator<<(ostream& os, const mint& a) { return os << a.x;}
 ll modd = 1e9+ 7;
ll wa (ll n,ll mi, ll ma){
    ll ans  = n * (mi+ma) /2;
    return ans;
}
int r5 (int a){
    int x = a * a * a * a * a;
    return x;
}

struct  Edge {int to,id;};

vector<vector<Edge>> g;
vector<int> ans;

void dfs(int v,int c = -1, int p = -1){
    int k = 1;
    REP(i,g[v].size()){
        int u = g[v][i].to, ei = g[v][i].id;
        if(u == p ) continue;
        if(c == k) k++;
        ans[ei] = k; k++;
        dfs(u,k-1,v);

    }
}


int main(){
    ll n,ans;
    string s;
    cin >> n >> s;
    
    vector<char> k;
    for(auto c :s){
        k.push_back(c);
        if(k.size() >= 3 && k[k.size()-3] =='f' && k[k.size()-2] == 'o' && k[k.size()-1] == 'x'){
            k.pop_back();
            k.pop_back();
            k.pop_back();
        }
    }
    cout << k.size() <<endl;
}




#include<bits/stdc++.h>
using namespace std;
using namespace std::chrono; 
const int mod=1e9+7;
const int mex=300005;
#define ll long long 
#define test int t;cin>>t;while(t--)
#define fast  ios_base::sync_with_stdio(false);cin.tie(NULL);
#define fo(i,a,n) for(int i=a;i<n;i++)
#define rfo(i,a,b) for(int i=a;i>=b;i--)
#define bg begin()
#define en end()
#define fi first
#define se second
#define ub upper_bound
#define lb lower_bound
#define pb push_back
#define veci vector<int>
#define veclli vector<long long int> 
#define all(x) x.begin(),x.end()
#define sci(x) scanf("%d",&x);
#define scc(x) scanf("%c",&x);
#define scs(x) scanf("%s",x);
#define debug(arr,n) for(int i=0;i<n;i++) printf("%d ",arr[i]);
#define sz(x) x.size()
#define loop(x) for(auto it=x.begin();it!= x.end();it++) 

int main()
{
    int n;
    cin>>n;
    string s;
    cin>>s;
    stack<char> st;
    fo(i,0,sz(s))
    {
        if(sz(st)<2) st.push(s[i]);
        else if(s[i]=='x')
        {
            char y=st.top();
            st.pop();
            char y1=st.top();
            st.pop();
            if(y1=='f'&&y=='o') continue;
            else {
                st.push(y1);
                st.push(y);
                st.push(s[i]);
            }
        }
        else st.push(s[i]);
    }
    cout<<sz(st)<<endl;
   
}