Submission #1167887

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Source Code Expand

#include <bits/stdc++.h> 

using namespace std;

long long x;

int main (int argc, char const *argv[]) {
	cin >> x;
	long long l = 0, r = 3e9 + 10;
	while (l < r) {
		long long z = l + r + 1 >> 1;
		if (z * (z + 1) > x + x) r = z - 1;
		else l = z;
	}
	if (l * (l + 1) == x + x) {
		printf("%lld\n", l);
		return 0;
	}
	long long extra = x - l * (l - 1) / 2;
	long long up = (l + 2) * (l + 1) / 2 - x;
	printf("%lld\n", min(extra, 2 * up + l + 1));
  return 0;
}

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