二分

#include <iostream>
#include <cstdio>
using namespace std;
int a[100005];
int find(int left, int right, int val){
	//cout << left << ' ' << right << endl;
	if(left * 1ll * (left + 1) / 2 > val || right * 1ll * (right + 1) / 2 < val) return -1;
	if(left >= right - 1) return left;
	int mid = (left + right) >> 1;
	return max(find(left, mid, val), find(mid, right, val));
}
int main(){
	int n;
	cin >> n;
	if(n == 1){
		cout << "1/1";
		return 0;
	}
	int sum = find(1, n - 1, n - 1) + 1;
	int m = n - sum * (sum - 1) / 2;
	int k = sum - m + 1;
	if(sum % 2) swap(m, k);
	cout << m << '/' << k;

	return 0;
}