#include<iostream>
#include<cstdio>
#define MAXN 500001
using namespace std;
int n,l,r;
int A[MAXN]={0};
int son=0;
int mother=0;
int gcd(int a,int b)
{
	if(b==0)
	return a;
	else
	return gcd(b,a%b);
}
int main()
{
	freopen("xgame.in","r",stdin);
	freopen("xgame.out","w",stdout);
	cin>>n>>l>>r;
	for(int i=1;i<=n;i++)
	{
		cin>>A[i];
	}
	int cnt=n;
	for(int i=1;i<=n;i++)
	{
		int tmp=0;
		int sum=0;
		for(int j=0;j<=n-i;j++)
		{
			mother++;
			sum+=A[i+j];
			tmp++;
			int ans=sum/tmp;
			if(ans>=l&&ans<=r)
			{
				son++;
			}
		}
	}
	if(son==0||mother==0)
	{
		cout<<"0"<<endl;
		return 0;
	}
	if(son==mother)
	{
		cout<<"1"<<endl;
		return 0;
	}
	int num=gcd(mother,son);
	mother/=num;
	son/=num;
	cout<<son<<"/"<<mother<<endl;
	return 0;
}