Submission #1592814

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Source Code Expand

// 等差数列の和の公式
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cctype>
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <string>
#include <sstream>
#include <vector>
#include <map>
#include <set>
#include <complex>
#include <functional>
#include <utility>

#define REP(i, n) for(int i = 0; i < (int)(n); ++i)
#define FOR(i, m, n) for(int i = (m); i < (int)(n); ++i)
#define ALL(x) (x).begin(), (x).end()
#define INF 2000000000
//#define int long long int

#ifdef LOCAL
  #define eprintf(...) fprintf(stdout, __VA_ARGS__)
#else
  #define eprintf(...) 0
#endif

using namespace std;

typedef long long LL;
typedef unsigned long long ULL;
typedef unsigned int uint;

int main() {
  int x;
  cin >> x;
  int sum;
  FOR(i, 1, x+1) {
    sum = (1 + i) * i / 2;
    if(sum >= x) {
      cout << i << endl;
      return 0;
    }
  }

  return 0;
}

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