比较暴力的做法

#include <bits/stdc++.h>
using namespace std;
int main(){
int n;
cin>>n;
int k=1;
while(k*(k+1)/2<n){
k++;
}
int m=n-k*(k-1)/2;
if(k%2==0){
cout <<m<<"/"<<(k+1-m)<<endl;
}else{
cout << (k+1-m) <<"/"<<m<<endl;
}
return 0;
}