#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define FI(x) freopen(x".in","r",stdin);
#define FO(x) freopen(x".out","w",stdout);
using namespace std;
const int maxn=500010;

int n,l,r,a[maxn],L,R,fst,ans=0,all,d;

int gcd(int a,int b)
{
    return b?gcd(b,a%b):a;
}

void RD(int& x)
{
    char c=' '; x=0;
    while(c<'0' || c>'9') c=getchar();
    while(c>='0' && c<='9') {x=x*10+c-'0';c=getchar();}
}

class input{
public:
    input & operator >>(int & i){
        RD(i);
        return *this;
    }
}scan;

int main()
{
    FI("xgame");
    FO("xgame");
    scan>>n>>L>>R;
    all=(n+1)*n>>1;l=L<<1,r=R<<1;
    if(all==0)
    {
        printf("0\n");
        return 0;
    }
    for(int i=1;i<=n;++i) {scan>>a[i];
        if(a[i]>=L && a[i]<=R) ++ans;}
    fst=a[1];
    for(int k=2;k<=n;l+=L,r+=R,++k)
    {
        fst+=a[k];
        for(int i=k,t=fst;i<=n;++i,t+=a[i]-a[i-k])
            if(t>=l && t<=r) ++ans;
    }
    d=gcd(ans,all);
    ans/=d,all/=d;
    if(all==1) printf("1\n");
    else printf("%d/%d\n",ans,all);
    
    return 0;
}
/*
4 2 3
3 1 2 4

*/