#include <iostream>
using namespace std;
int main()
{
int n = 1, s = 0, m;
cin >> m;
while (true)
{
s += n;
if (s > m)
break;
n++;
}
cout << n;
return 0;
}
int ans1()
{
int n = 1, s = 0, m;
cin >> m;
while (s <= m)
{
s += n;
n++;
}
cout << n - 1;
return 0;
}