#include <bits/stdc++.h>
#define ALL(x) (x).begin(),(x).end()
using namespace std;
using ll = long long int;
using ull = unsigned long long int;
const ll INF=LLONG_MAX;
const int inf=INT_MAX;
const ull md=1000000000;//10^9

void out(int ans){
  cout << ans << endl;
  exit(0);
}

int main(){
  ios_base::sync_with_stdio(false);  
  cin.tie(nullptr);
  cout.tie(nullptr);

  int N;
  cin >> N;
  for(int i=1; ; i++){
    if(1+(1+i)*i/2 > N){
      cout << i << endl;
      break;
    }
  }
  return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main() {
string a, saida = "";
cin >> a;

int i = 0;
while(a[i] != '.' && i < a.length()){
    saida += a[i];
    i++;
}
cout << saida << endl;



return 0;
}
