建议加强，见离普代码

#include<bits/stdc++.h>
using namespace std;
int n,a=1,b=1,sum=2,ab=1;
int main(){
	cin>>n;
	for(int i=0;i<n;i++){
		if(a+b==sum&&(a==1&&sum%2==1 || b==1&&sum%2==0)){
			if(a+b==sum&&i==ab){
				if(ab==0){
					a=sum;
					b=1;
					
				}else{
					b=sum;
					a=1;
					
				}
				ab+=sum;
				sum++;
			}
		}else if(sum%2==0){
			a++;b--;
		}else if(sum%2==1){
			a--;b++;
		}
		
	}
	cout<<b<<"/"<<a;
	return 0;
}