Submission #1790678

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Source Code Expand

#include <assert.h>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <climits>
#include <algorithm>
#include <numeric>
#include <functional>
#include <iostream>
#include <string>
#include <array>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <complex>
#include <bitset>
typedef long long ll;
typedef unsigned long long ull;

#define REP(i, n) for (int i = 0; i < n; i++)
#define REPR(i, n) for (int i = n; i >= 0; i--)
#define DEBUG(vec) for (auto v : vec) { cout << v << " "; } cout << endl;

using namespace std;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  ll N;
  cin >> N;

  ll cur = 0;
  REP(i, N + 1) {
    cur += i;
    if (cur >= N) {
      cout << i << endl;
      return 0;
    }
  }
  return 0;
}

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