#include <bits/stdc++.h>
                            #include<iostream>
                            #include<cstdio>
                            #include<vector>
                            #include<queue>
                            #include<map>
                            #include<cstring>
                            #include<string>
                            #include <math.h>
                            #include<algorithm>
                        //    #include <boost/multiprecision/cpp_int.hpp>
                            #include<functional>
                     #define int long long
                            #define inf  1000000007
                            #define pa pair<int,int>
                            #define ll long long
                            #define pal pair<double,int>
                            #define ppa pair<string,pa>
                            #define ssa pair<string,int>
                            #define  mp make_pair
                            #define  pb push_back
                            #define EPS (1e-10)
                            #define equals(a,b) (fabs((a)-(b))<EPS)
                     
                            using namespace std;
                     //priority_queue<int, vector<int>, greater<int> > que;
                            class Point{
                            	public:
                            	double x,y;
                            	Point(double x=0,double y=0):x(x),y(y) {}
                            	Point operator + (Point p) {return Point(x+p.x,y+p.y);}
                            	Point operator - (Point p) {return Point(x-p.x,y-p.y);}
                            	Point operator * (double a) {return Point(x*a,y*a);}
                            	Point operator / (double a) {return Point(x/a,y/a);}
                            	double absv() {return sqrt(norm());}
                            	double norm() {return x*x+y*y;}
                            	bool operator < (const Point &p) const{
                            		return x != p.x ? x<p.x: y<p.y;
                            	}
                            	bool operator == (const Point &p) const{
                            		return fabs(x-p.x)<EPS && fabs(y-p.y)<EPS;
                            	}
                            };
                            typedef Point Vector;
                     
                            struct Segment{
                            Point p1,p2;
                            };
                     
                        double hen(Vector a){
                        if(fabs(a.x)<EPS && a.y>0) return acos(0);
                        else if(fabs(a.x)<EPS && a.y<0) return 3*acos(0);
                        else if(fabs(a.y)<EPS && a.x<0) return 2*acos(0);
                        else if(fabs(a.y)<EPS && a.x>0) return 0.0;
                        else if(a.y>0) return acos(a.x/a.absv());
                        else return 2*acos(0)+acos(-a.x/a.absv());
                     
                        }
                     
                string itos( int i ) {
                ostringstream s ;
                s << i ;
                return s.str() ;
                }
                 
                int gcd(int v,int b){
                	if(v>b) return gcd(b,v);
                	if(v==b) return b;
                	if(b%v==0) return v;
                	return gcd(v,b%v);
                }
                            double dot(Vector a,Vector b){
                            	return a.x*b.x+a.y*b.y;
                            }
                            double cross(Vector a,Vector b){
                            	return a.x*b.y-a.y*b.x;
                            }
                        
                double distans(double x1,double y1,double x2,double y2){
                	double rr=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
                	return sqrt(rr);
                	
                }

                            //----------------kokomade tenpure------------
int N=262144;
pa sgt[530000];

pa minis(int i,int j ){
if(i==j) return sgt[i];
	else if(i%2==1){
		pa z=minis(i+1,j);
		if(sgt[i].first>z.first)return sgt[i] ;
		else return z;
	}
		else if(j%2==0) 	{
		pa z=minis(i,j-1);
		if(sgt[j].first>z.first)return sgt[j] ;
		else return z;
	}
else return minis(i/2,j/2);
}

pa sgtmin(int i ,int j) {
	return minis(i+N,j+N);
}

void upd(int x,int y){
	x+=N;
sgt[x].first=y;
	sgt[x].second=x;
x=x/2;
while(x != 0){
	if(sgt[2*x+1].first>sgt[2*x].first){
		sgt[x]=sgt[2*x+1];
	}
	else sgt[x]=sgt[2*x];

x=x/2;
}
}

vector<int> G[100002];
 

vector<int> ki;
vector<int> ni;
vector<int> koritu;
int n,m;
int sumi[100002]={0};
int guuki[100002]={0};
int kich,saizu;


void dfs(int r,int kyo){
//	cout<<r<<endl;
	int y=G[r].size();
	if(y==0){
		saizu=1;
		sumi[r]=1;
		return;
	}
	guuki[r]=kyo;
	saizu++;
	sumi[r]=1;
	for(int i=0;i<y;i++){
		if(sumi[G[r][i]]==1){
			if((kyo+1)%2  != guuki[G[r][i]] %2) kich=1;
		}
		else{
//			cout<<"dfs "<<G[r][i]<<endl;
			dfs(G[r][i],kyo+1);
	}
	}
	return;
}

 signed  main(){
int n;
 	cin>>n;
 	
 	int i,sum=0;
 	for(i=0;i<10000000;i++){
 		sum += i;
 		if(sum>=n) break;
 	}
 	cout<<i<<endl;
 	//  	printf("%.10f\n",ans[n-1]);
                    	return 0;
}

Measured memory_bytes: 2816