C++ :

#include<iostream>
using namespace std;
int main()
{
	long h,fz,fm,n,sum=0;
	cin>>n;
	h=0;
	sum=0;
	while(sum<n)
	{
		h++;
		sum+=h;		
	}
	sum-=h;
	int m;//表示第m项
	m=n-sum;
	if(h&1)
	{
		fm=m;
		fz=h+1-m;
	} 
	else
	{
		fz=m;
		fm=h+1-m;
	}
	cout<<fz<<'/'<<fm<<endl;
	return 0;
}

Pascal :

var
  n,i,a,b:longint;flag:boolean;
function w(i:longint):longint;
var
  j:longint;
begin
  w:=0;
  for j:=1 to i do
    w:=w+j;
end;
begin
  read(n);
  for i:=1 to 1000 do begin
    if n<=w(i) then begin a:=i;n:=n-w(i-1);break;end;
  end;
  if a mod 2=0 then flag:=false else flag:=true;
  b:=1;
  if flag then begin
  for i:=a downto 1 do begin
    if b=n then begin writeln(i,'/',a-i+1);halt;end  else inc(b);
  end;end
  else begin
         for i:=1 to a do begin
         if b=n then begin writeln(i,'/',a-i+1);halt;end else inc(b);
       end;
  end;
end.