#include <iostream>
#include <cstdio>
#include <cstdlib>

using std::cin;
using std::cout;
using std::endl;

int n,l,r,s[500001];
int now = 0;
int cases;
int total;
double avg;

int main(int argc,char ** argv){
	int tmp;
	freopen("xgame.in","r",stdin);
	freopen("xgame.out","w+",stdout);
	cin>>n>>l>>r;
	for(int x=1;x<=n;x++){
		cin>>tmp;
		s[x] = s[x-1] + tmp;
	}
	for(int x=1;x<=n;x++){
	    for(int y=x;y<=n;y++){
            avg = (s[y] - s[x-1])/(y-x+1);
	        //cout<<x<<" "<<y<<endl;
	        //cout<<"avarage "<<avg<<endl;
	        cases++;
	        if(avg>=l&&avg<=r) total ++;
	    }
	}
	if(total==cases){
		cout<<1<<endl;
		return 0;
	}else if(!total){
		cout<<0<<endl;
		return 0;
	}
	for(int x=2;x<=total;x++){
		if(total%x==0&&cases%x==0){
			total /=x;
			cases /=x;
		}
	}
	cout<<total<<'/'<<cases<<endl;
	return 0;
}