洛谷P1494

#include <bits/stdc++.h>
/*
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/hash_policy.hpp>
*/
using namespace std;

const double eps = 1e-10;
const double pi = 3.1415926535897932384626433832795;
const double eln = 2.718281828459045235360287471352;

#define f(i, a, b) for (int i = a; i <= b; i++)
#define scan(x) scanf("%d", &x)
#define mp make_pair
#define pb push_back
#define lowbit(x) (x&(-x))

#define fi first
#define se second
#define SZ(x) int((x).size())
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define summ(a) (accumulate(all(a), 0ll))

typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef vector<int> vi;

using ll=long long;

ll n,m,k,a[(int)5e4+9],ans[(int)5e4+9],l=1,r,sum,s[(int)5e4+9],sz,id[(int)5e4+9],l1[(int)5e4+9],r1[(int)5e4+9];
struct line{
    ll l,r,num;
}q[(int)5e4+9];
bool cmp(line x,line y){
    return id[x.r]==id[y.r]?x.l<y.l:x.r<y.r;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin>>n>>m;
    sz=n/sqrt(m*2/3);
    for(int i=1;i<=n;++i)cin>>a[i],id[i]=(i-1)/sz+1;
    for(int i=1;i<=m;++i)cin>>q[i].l>>q[i].r,q[i].num=i,l1[i]=q[i].l,r1[i]=q[i].r;
    sort(q+1,q+1+m,cmp);
    for(int i=1;i<=m;++i){
        while(l<q[i].l)sum-=s[a[l]]*(s[a[l]]-1)/2,s[a[l]]-=1,sum+=s[a[l]]*(s[a[l]]-1)/2,l+=1;
        while(l>q[i].l)l-=1,sum-=s[a[l]]*(s[a[l]]-1)/2,s[a[l]]+=1,sum+=s[a[l]]*(s[a[l]]-1)/2;
        while(r<q[i].r)r+=1,sum-=s[a[r]]*(s[a[r]]-1)/2,s[a[r]]+=1,sum+=s[a[r]]*(s[a[r]]-1)/2;
        while(r>q[i].r)sum-=s[a[r]]*(s[a[r]]-1)/2,s[a[r]]-=1,sum+=s[a[r]]*(s[a[r]]-1)/2,r-=1;
        ans[q[i].num]=sum;
    }
    for(int i=1,x;i<=m;++i){
        x=std::gcd(ans[i],(r1[i]-l1[i]+1)*(r1[i]-l1[i])/2);
        if(l1[i]==r1[i])cout<<"0/1\n";
        else cout<<ans[i]/x<<"/"<<(r1[i]-l1[i]+1)*(r1[i]-l1[i])/2/x<<"\n";
    }
    return 0;
}