#include <bits/stdc++.h>
using namespace std;
#define fastio ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
#define lli long long int
#define tc int t;cin>>t;while(t--)
#define all(x) x.begin(),x.end()
#define f first
#define s second
#define pb push_back
#define pi pair<int,int>
#define pll pair<lli,lli>
#define vi vector<int>
#define vll vector<lli>
#define vpi vector<pair<int,int> > 
#define vpll vector<pair<lli,lli> > 
#define vvi vector<vector<int> >
#define vvll vector<vector<lli> >
#define vvpi vector<vector<pair<int,int> > >
#define vvpll vector<vector<pair<lli,lli> > >
#define inf 1000000000
#define maxn 1005
lli mod=998244353;

int main(){
    fastio;
    lli n;
    cin>>n;
    lli sm=0;
    for(int i=1;i<=n;i++){
        sm+=i;
        if(sm>=n)
        {
            cout<<i<<"\n";
            break;
        }
    }
	return 0;
}

#include<bits/stdc++.h>
//#include<ext/pb_ds/assoc_container.hpp>
//#include<ext/pb_ds/tree_policy.hpp>
//#include <ext/pb_ds/trie_policy.hpp>
//using namespace __gnu_pbds;
using namespace std;
#define ll 				long long int
#define ld				long double
#define mod             1000000007
#define inf             1e18
#define endl			"\n"
#define pb 				push_back
#define vi              vector<int>
#define vl              vector<ll>
#define vs				vector<string>
#define pii             pair<ll,ll>
#define ump				unordered_map
#define mp 				make_pair
#define pq_max          priority_queue<ll>
#define pq_min          priority_queue<ll,vi,greater<ll> >
#define all(n) 			n.begin(),n.end()
#define ff 				first
#define ss 				second
#define mid(l,r)        (l+(r-l)/2)
#define bitc(n) 		__builtin_popcount(n)
#define loop(i,a,b) 	for(int i=(a);i<=(b);i++)
#define looprev(i,a,b) 	for(int i=(a);i>=(b);i--)
#define iter(container, it) for(__typeof(container.begin()) it = container.begin(); it != container.end(); it++)
#define log(args...) 	{ string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args); }
#define logarr(arr,a,b)	for(int z=(a);z<=(b);z++) cout<<(arr[z])<<" ";cout<<endl;
#define M 		1000000007
#define w(x)            int x; cin>>x; while(x--)
template <typename T> T gcd(T a, T b) {if (a % b) return gcd(b, a % b); return b;}
template <typename T> T lcm(T a, T b) {return (a * (b / gcd(a, b)));}
vs tokenizer(string str, char ch) {std::istringstream var((str)); vs v; string t; while (getline((var), t, (ch))) {v.pb(t);} return v;}


void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
	cout << *it << " = " << a << endl;
	err(++it, args...);
}
//typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> pbds;
//typedef trie<string,null_type,trie_string_access_traits<>,pat_trie_tag,trie_prefix_search_node_update> pbtrie;



void file_i_o()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
}

ll calc(ll k) {

	return k * (k + 1) / 2;
}



int main(int argc, char const *argv[]) {
	clock_t begin = clock();
	file_i_o();
	// Write your code here....
	ll n;
	cin >> n;


	loop(i, 1, n) {

		if (calc(i) >= n) {

			cout << i << endl;
			break;
		}


	}



#ifndef ONLINE_JUDGE
	clock_t end = clock();
	cout << "\n\nExecuted In: " << double(end - begin) / CLOCKS_PER_SEC * 1000 << " ms";
#endif
	return 0;
}







