#include <bits/stdc++.h>

using namespace std;

#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")

using ll = long long;
using ld = long double;



#define mp make_pair

int p = 1e9 + 7;

int mul(int a, int b) {
    return (1LL * a * b) % p;
}

int add(int a, int b) {
    int s = (a+b);
    if (s>=p) s-=p;
    return s;
}

int sub(int a, int b) {
    int s = (a+p-b);
    if (s>=p) s-=p;
    return s;
}

int po(int a, int deg)
{
    if (deg==0) return 1;
    if (deg%2==1) return mul(a, po(a, deg-1));
    int t = po(a, deg/2);
    return mul(t, t);
}

int inv(int n)
{
    return po(n, p-2);
}


mt19937 rnd(time(0));


const int N = 1000005;

vector<int> facs(N), invfacs(N);

void init()
{
    facs[0] = 1;
    for (int i = 1; i<N; i++) facs[i] = mul(facs[i-1], i);
    invfacs[N-1] = inv(facs[N-1]);
    for (int i = N-2; i>=0; i--) invfacs[i] = mul(invfacs[i+1], i+1);
}

int C(int n, int k)
{
    if (n<k) return 0;
    if (n<0 || k<0) return 0;
    return mul(facs[n], mul(invfacs[k], invfacs[n-k]));
}




/*struct DSU
{
    vector<int> sz;
    vector<int> parent;

    void make_set(int v) {
        parent[v] = v;
        sz[v] = 1;
    }

    int find_set(int v) {
        if (v == parent[v])
            return v;
        return parent[v] = find_set(parent[v]);
    }

    void union_sets(int a, int b) {
        a = find_set(a);
        b = find_set(b);
        if (a != b) {
            if (sz[a] < sz[b])
                swap(a, b);
            parent[b] = a;
            sz[a] += sz[b];
        }
    }

    DSU (int n)
    {
        parent.resize(n);
        sz.resize(n);
        for (int i = 0; i<n; i++) make_set(i);
    }
};*/


int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr);

    int n; cin>>n;
    string s;
    cin>>s;
    vector<char> a(2e5);
    int cur = 0;
    for (auto c: s)
    {
        a[cur] = c;
        if (cur>=2 && a[cur-2]=='f' && a[cur-1]=='o' && a[cur]=='x') cur-=3;
        cur++;
    }
    cout<<cur;
}


#include <iostream>
#include <stdio.h>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <cstring>
#include <algorithm>
#include <math.h>

using namespace std;

typedef long long ll;
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;

#define FOR(i,n,m) for(int i=n; i<(int)m; i++)
#define ROF(i,n,m) for(int i=n; i>(int)m; i--)
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define F first
#define S second
#define ri(a) scanf("%d",&a)
#define rii(a,b) ri(a),ri(b)
#define riii(a,b,c) rii(a,b),ri(c)
#define lri(a) scanf("%lld",&a)
#define lrii(a,b) lri(a),lri(b)
#define ms(obj,val) memset(obj,val,sizeof(obj))
#define all(x) x.begin(),x.end()
#define debug true
#define dprintf debug && printf

const int INF = 0x3f3f3f3f;
const ll INFLL = 1e18;
const int MOD = 1e9+7;
const int MAXN = 2e5+5;

char s[MAXN];
int n;

int main(){
    //ios_base::sync_with_stdio(false);
    //cin.tie(NULL);

    ri(n);
    scanf("%s", s);

    vector<char> ans;
    int sz = 0;
    FOR(i,0,n){
        ans.pb(s[i]); sz++;
        if(s[i] == 'x' && sz > 2 
            && ans[sz-2] == 'o' && ans[sz-3] == 'f'){
                ans.pop_back();
                ans.pop_back();
                ans.pop_back();
                sz -= 3;
            }
    }

    printf("%d\n", sz);

    return 0;
}
