#include<bits/stdc++.h>
#define rep(i,a,...) for(int i = (a)*(strlen(#__VA_ARGS__)!=0);i<(int)(strlen(#__VA_ARGS__)?__VA_ARGS__:(a));++i)
#define per(i,a,...) for(int i = (strlen(#__VA_ARGS__)?__VA_ARGS__:(a))-1;i>=(int)(strlen(#__VA_ARGS__)?(a):0);--i)
#define foreach(i, n) for(auto &i:(n))
#define all(x) (x).begin(), (x).end()
#define bit(x) (1ll << (x))
#define lambda(RES_TYPE, ...) (function<RES_TYPE(__VA_ARGS__)>)[&](__VA_ARGS__) -> RES_TYPE
#define method(FUNC_NAME, RES_TYPE, ...) function<RES_TYPE(__VA_ARGS__)> FUNC_NAME = lambda(RES_TYPE, __VA_ARGS__)
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
//const ll MOD = (ll)1e9+7;
const ll MOD = 998244353;
const int INF = (ll)1e9+7;
const ll INFLL = (ll)1e18;
template<class t>
using vvector = vector<vector<t>>;
template<class t>
using vvvector = vector<vector<vector<t>>>;
template<class t>
using priority_queuer = priority_queue<t, vector<t>, greater<t>>;
template<class t, class u> bool chmax(t &a, u b){if(a<b){a=b;return true;}return false;}
template<class t, class u> bool chmin(t &a, u b){if(a>b){a=b;return true;}return false;}
#ifdef DEBUG
#define debug(x) cout<<"LINE "<<__LINE__<<": "<<#x<<" = "<<x<<endl;
#else
#define debug(x) (void)0
#endif

namespace templates{
  ll modpow(ll x, ll b,ll mod=MOD){
    ll res = 1;
    while(b){
      if(b&1)res = res * x % mod;
      x = x * x % mod;
      b>>=1;
    }
    return res;
  }

  ll modinv(ll x){
    return modpow(x, MOD-2);
  }

  bool was_output = false;
  template<class t>
  void output(t a){
    if(was_output)cout << " ";
    cout << a;
    was_output = true;
  }
  void outendl(){
    was_output = false;
    cout << endl;
  }
  ll in(){
    ll res;
    cin >> res;
    return res;
  }

  template<class t>
  istream& operator>>(istream&is, vector<t>&x){
    for(auto &i:x)is >> i;
    return is;
  }

  template<class t, class u>
  istream& operator>>(istream&is, pair<t, u>&x){
    is >> x.first >> x.second;
    return is;
  }

  template<class t>
  t in(){
    t res; cin >> res; return res;
  }

  template<class t>
  void out(t x){
    cout << x;
  }

  template<class t>
  vector<t> sorted(vector<t> line,function<bool(t,t)> comp=[](t a,t b){return a<b;}){
    sort(line.begin(),line.end(),comp);
    return line;
  }

  template<class t>
  vector<t> reversed(vector<t> line){
    reverse(line.begin(),line.end());
    return line;
  }
}

using namespace templates;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    ll n = in();
    ll lp = 1;
    ll rp = min<ll>(sqrt(n)*2 + 10,n+1);
    while(lp<rp){
        ll mid = (lp + rp) / 2;
        if(mid * (mid+1) / 2 <= n+1){
            lp = mid + 1;
        }else{
            rp = mid;
        }
    }
    cout << n - lp + 2 << endl;
  return 0;
}


#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization ("unroll-loops")

#include<bits/stdc++.h>
#include<string.h>
using namespace std;
#define pb      push_back
#define all(v)  v.begin(),v.end()
#define see(x)  cout<<endl<<#x<<" : "<<(x)<<endl;
#define ya      cout<<"YES"<<endl;
#define no      cout<<"NO"<<endl;
#define ff      first
#define sc      second
#define inf     999999999
#define pi      3.14159265359
inline  int     random(int a=1,int b=10){return a+rand()%(b-a+1);}
typedef long long ll;
typedef pair<int,int> pii;
const int N=500009;

int main()
{
//    ios::sync_with_stdio(0);
//    cin.tie(0);

    ll n,ans=0,i,j,k,f=0,o=0,x=0;

    cin>>n;

    string s;

    cin>>s;

    ans=n;

    stack<char>q;

    for(i=0;i<n;i++)
    {
        if(s[i]=='x')
        {
            if(q.size()>=2)
            {
                char c=q.top();
                q.pop();
                char d=q.top();
                q.pop();
//                see(c)
//                see(d)
                if(c=='o' && d=='f')
                {
                    ans-=3;
                }
                else
                {
                     while(!q.empty())
                     {
                         q.pop();
                     }
                }
            }
            else
            {
                while(!q.empty())
                {
                    q.pop();
                }
            }
            continue;
        }
        if(s[i]=='f')q.push(s[i]);
        else if(s[i]=='o')q.push(s[i]);
        else
        {
            while(!q.empty())
            {
                q.pop();
            }
        }
    }

    cout<<ans<<endl;

    return 0;
}

