#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,i=0,s=0;
    cin>>n;
    while(1){
        i++;
        s+=i;
        if(s>=n){
            break;
        }   
    }
    cout<<i;
    return 0;
}
/**************************************************************
	Problem: 1248
	User: zhangziang
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/