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| const int sz = 700;
const int maxn = 100000 + 5;
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
PII get(ll a, ll b) {
if (a == 0) return { 0, 1 };
ll g = gcd(a, b);
return { a / g, b / g };
}
struct Que {
int l, r, id;
bool operator<(const Que& b) const {
if (l / sz == b.l / sz) {
if ((l / sz) % 2) return r > b.r;
else return r < b.r;
}
return l < b.l;
}
} q[maxn];
int n, m, a[maxn];
PII ans[maxn];
ll fz, bag[maxn];
ll cal(ll x) {
return x * (x - 1) / 2;
}
void update(int x, int t) {
fz -= cal(bag[x]);
bag[x] += t;
fz += cal(bag[x]);
}
int main() {
scanf("%d%d", &n, &m);
for (int i = 1; i <= n; i++) scanf("%d", a + i);
for (int i = 1; i <= m; i++) scanf("%d%d", &q[i].l, &q[i].r), q[i].id = i;
sort(q + 1, q + 1 + m);
int l = 1, r = 0;
for (int i = 1; i <= m; i++) {
while (r < q[i].r) update(a[++r], 1);
while (l > q[i].l) update(a[--l], 1);
while (l < q[i].l) update(a[l++], -1);
while (r > q[i].r) update(a[r--], -1);
dbg(q[i].l, q[i].r, l, r);
ans[q[i].id] = get(fz, cal(r - l + 1));
}
for (int i = 1; i <= m; i++) {
printf("%lld/%lld\n", ans[i].first, ans[i].second);
}
return 0;
}
|