//枚举起点
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
void read(int & x){
	char c;
	for(c=getchar();c<'0'||c>'9';c=getchar());
	for(x=0;c<='9'&&c>='0';c=getchar())
		x=x*10+(c-'0');
}//读入优化 
int a[500005];
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);
	int n,l,r;
	read(n),read(l),read(r);
	for(int i=1;i<=n;i++)
		read(a[i]);
	int yes=0,tot=(n+1)*n/2;
	for(int i=1;i<=n;i++){
		int sum=0;
		for(int j=i;j<=n;j++){
			sum+=a[j];
			if(sum/(j-i+1)<=r&&sum/(j-i+1)>=l)
				yes++;
		}
	}
	if(yes==0)printf("0\n");
	else if(yes==tot)printf("1\n");
	else {
		int k=gcd(yes,tot);
		printf("%d/%d",yes/k,tot/k);
	}
	return 0;
}