#include <bits/stdc++.h>
using namespace std;
long long factorial(long long n) {
  return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
}
long long gcd(long long a, long long b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
long long lcm(long long a, long long b) { return (a * b) / gcd(a, b); }
bool sortByVal(const pair<long long, long long> &a,
               const pair<long long, long long> &b) {
  return (a.second > b.second);
}
long long Powb(long long b, long long n) {
  if (n == 0) return 1LL;
  if (n == 1) return b;
  long long temp = Powb(b, n / 2);
  if (n % 2 == 0) {
    return (temp * temp) % 1000000007;
  } else {
    return (b * ((temp * temp) % 1000000007)) % 1000000007;
  }
}
long long sumofdigit(long long n) {
  long long c = 0, d = 0, sum = 0;
  while (n > 0) {
    c = n % 10;
    sum += c;
    n /= 10;
  }
  return sum;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  int t = 1;
  while (t--) {
    long long m, i, k, j, c = 0, d = 0, sum = 0, e = 0, f = 0, g = 0, h = 0, n,
                          maxi = 0;
    cin >> n;
    for (i = 1; i < 10000000000; i++) {
      sum += i;
      if (sum >= n) {
        break;
      }
    }
    sum -= i;
    cout << n - sum;
  }
}
