#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <atcoder/modint>


using namespace std;
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;
#define rep(i,n) for(int i=0; i<(int)(n); i++)


const i64 INF = 1001001001001001001;
using modint = atcoder::static_modint<998244353>;




int main(){
    vector<int> small_ans = {0,0,0,1,2,2,3,4};
    i64 N; cin >> N;
    if(N < small_ans.size()){
        cout << small_ans[N] << '\n';
        return 0;
    }

    auto countShade = [N](i64 showCnt) -> bool {
        i64 height = N - showCnt;
        height -= (N - 1 - height) * 2;
        for(i64 baseHeight = N; baseHeight >= N-showCnt+3; baseHeight--){
            height -= (N - 3 - height) * 2 + 1;
            if(height <= 0) return true;
        }
        return false;
    };

    i64 c = 1;
    while(!countShade(c)) c++;
    cout << (N-c) << '\n';

    return 0;
}


struct ios_do_not_sync{
    ios_do_not_sync(){
        std::ios::sync_with_stdio(false);
        std::cin.tie(nullptr);
    }
} ios_do_not_sync_instance;