#ifndef INCLUDED_MAIN
#define INCLUDED_MAIN

#include __FILE__

vector<ll> dx={-1,0,1};
vector<ll> dy={-1,0,1};

int main(){
    // squareだね
    ll n;
    cin>>n;
    ll ok=0;
    ll ng=n;
    while(ng-ok>1) {
        ll mid=(ng-ok)/2+ok;
        if(mid*mid<=n) ok=mid;
        else ng=mid;
    }
    cout<<ok<<endl;
}

#else
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define srep(i,l,r) for(int i=l;i<=r;i++)
using ll = long long;
#define mod 998244353ll
#define vout(v) for(auto i :v) cout<<i<<" ";
#define INF 922330000000000000ll
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define enld endl
#define Rn return
#define vl vector<ll>

bool isin(ll i,ll j,ll hgt,ll width) {
    if(i<0 || i>=hgt || j<0 || j>=width) return false;
    else return true;
}



ll lensum(ll l,ll r) {
    ll len=r-l+1;
    return (l-1)*len + (r-l+1)*(r-l+1)/2;
}
vector<ll> Erasieve(ll n) {
    vector<bool> is_prime(n+1, true);
    is_prime[0] = is_prime[1] = false; 

    for (int i=2;i*i<=n;++i) {
        if (is_prime[i]) {
            for (int j=i*i;j<=n;j+=i) is_prime[j] = false;
        }
    }
    vector<ll> primes;
    srep(i,2,n) {
        if (is_prime[i]) primes.push_back(i);
    }

    return primes;
}

ll divcount(ll n) {
    ll ans=0;
    for(int i=1;i*i<=n;i++) {
        if(n%i==0) ans+=(i*i==n ? 1:2);
    }
    return ans;
}
struct UnionFind {
    vector<int> par;  
    vector<int> rank;
    UnionFind(int N) : par(N), rank(N, 0) {
        for (int i = 0; i < N; i++) {
            par[i] = i;
        }
    }
    // 経路圧縮
    int root(int x) {
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }

    void unite(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        if (rx == ry) return; 
        if (rank[rx] < rank[ry]) {
            par[rx] = ry;
        } else {
            par[ry] = rx;
            if (rank[rx] == rank[ry]) {
                rank[rx]++;
            }
        }
    }

    bool same(int x, int y) {
        return root(x) == root(y);
    }
};



template <class T> void vecpr(T first,T last) {
    ll tmp=0;
    for(auto it=first;it!=last;++it) {
        if(tmp) cout<<" ";
        cout<<*it;
        tmp++;
    }
    cout<<endl;
}

template <class T> void vvpr(vector<vector<T>> a) {
    for(int i=0;i<(ll)a.size();i++) {
        for(int j=0;j<(ll)a[i].size();j++) {
            if(j) cout<<" ";
            cout<<a[i][j];
        }
        cout<<endl;
    }
}

vector<ll> slmax(vector<ll> a, ll limit, ll breadth) {//slidewindowによる幅breadthでの区間最大値評価,limit=a.size()
    deque<ll> deq;
    vector<ll> max_numbers(limit, (-1)*INF);
    rep(i, limit) {
        while (!deq.empty() && deq.front() <= i - breadth) deq.pop_front();
        while (!deq.empty() && a[deq.back()] <= a[i]) deq.pop_back();
        deq.push_back(i);
        max_numbers[i] = a[deq.front()];
    }
    return max_numbers;
}

vector<ll> slmin(vector<ll> a, ll limit, ll breadth) {//slidewindowによる幅breadthでの区間最小値評価,limit=a.size()
    deque<ll> deq;
    vector<ll> min_numbers(limit, INF);
    rep(i, limit) {
        while (!deq.empty() && deq.front() <= i - breadth) deq.pop_front();
        while (!deq.empty() && a[deq.back()] >= a[i]) deq.pop_back();
        deq.push_back(i);
        min_numbers[i] = a[deq.front()];
    }
    return min_numbers;
}


ll modpow(ll fl,ll po,ll mode) {  //mode0=modなし、mode1=あり
    ll ret=1;
    rep(i,po) {
        ret*=fl;
        if(mode) ret=(ret+mod)%mod;
    }
    return ret;
}
ll gcd(ll a,ll b) {  //Euclid
    if(a<b) return gcd(b,a);
    if(a%b==0) return b;
    return gcd(b,a%b);
}

vector<ll> lis_min(vector<ll> &a) { //最後まで見たときに、「長さiの最後尾は最小でいくつか？」を返す
    ll n=(ll)a.size();
    vector<ll> dp(n,INF);
    rep(i,n){
    auto itr = lower_bound(dp.begin(),dp.end(), a[i]);
    *itr = a[i]; 
    }
    return dp;
}//あんま使えない

void lis_min_update(vector<ll>& dp, ll x) { //↑を一回ごとに処理するやつ (cf.abc393-f);
    auto it=lower_bound(dp.begin(), dp.end(), x);
    if(it==dp.end())
        dp.push_back(x);
    else 
        *it=x;
}




vector<ll> lis_size(vector<ll>& a ,vector<ll>&seqcopy) { // 最長増加部分列の a index目までみた時点の長さがdp[i]
    ll n=a.size();
    vector<ll> dp(n,1);  
    vector<ll> seq;       

   rep(i,n) {
        auto it=lower_bound(seq.begin(), seq.end(), a[i]);
        
        if (it==seq.end())  seq.push_back(a[i]);
        else *it=a[i];
        dp[i]=distance(seq.begin(), lower_bound(seq.begin(), seq.end(), a[i]))+1;
    }
    srep(i,1,n-1) {
        if(dp[i]<dp[i-1]) dp[i]=dp[i-1];
    }
    seqcopy=seq;
    return dp;
}



#endif