cf522d WA

#include <assert.h>
#include <bits/stdc++.h>
using namespace std;
#define dbg(...) logger(#__VA_ARGS__, __VA_ARGS__)
template <typename... Args> void logger(string vars, Args &&...values)
{
    cerr << vars << " = ";
    string delim = "";
    (..., (cerr << delim << values, delim = ", "));
    cerr << endl;
}

namespace atcoder
{

template <class S, S (*op)(S, S), S (*e)()> struct segtree {
    int ceil_pow2(int n)
    {
        int x = 0;
        while ((1U << x) < (unsigned int) (n))
            x++;
        return x;
    }

  public:
    segtree() : segtree(0) {}
    explicit segtree(int n) : segtree(std::vector<S>(n, e())) {}
    explicit segtree(const std::vector<S> &v) : _n(int(v.size()))
    {
        log = ceil_pow2(_n);
        size = 1 << log;
        d = std::vector<S>(2 * size, e());
        for (int i = 0; i < _n; i++)
            d[size + i] = v[i];
        for (int i = size - 1; i >= 1; i--) {
            update(i);
        }
    }

    void set(int p, S x)
    {
        assert(0 <= p && p < _n);
        p += size;
        d[p] = x;
        for (int i = 1; i <= log; i++)
            update(p >> i);
    }

    S get(int p) const
    {
        assert(0 <= p && p < _n);
        return d[p + size];
    }

    S prod(int l, int r) const
    {
        assert(0 <= l && l <= r && r <= _n);
        S sml = e(), smr = e();
        l += size;
        r += size;

        while (l < r) {
            if (l & 1)
                sml = op(sml, d[l++]);
            if (r & 1)
                smr = op(d[--r], smr);
            l >>= 1;
            r >>= 1;
        }
        return op(sml, smr);
    }

    S all_prod() const { return d[1]; }

    template <bool (*f)(S)> int max_right(int l) const
    {
        return max_right(l, [](S x) { return f(x); });
    }
    template <class F> int max_right(int l, F f) const
    {
        assert(0 <= l && l <= _n);
        assert(f(e()));
        if (l == _n)
            return _n;
        l += size;
        S sm = e();
        do {
            while (l % 2 == 0)
                l >>= 1;
            if (!f(op(sm, d[l]))) {
                while (l < size) {
                    l = (2 * l);
                    if (f(op(sm, d[l]))) {
                        sm = op(sm, d[l]);
                        l++;
                    }
                }
                return l - size;
            }
            sm = op(sm, d[l]);
            l++;
        } while ((l & -l) != l);
        return _n;
    }

    template <bool (*f)(S)> int min_left(int r) const
    {
        return min_left(r, [](S x) { return f(x); });
    }
    template <class F> int min_left(int r, F f) const
    {
        assert(0 <= r && r <= _n);
        assert(f(e()));
        if (r == 0)
            return 0;
        r += size;
        S sm = e();
        do {
            r--;
            while (r > 1 && (r % 2))
                r >>= 1;
            if (!f(op(d[r], sm))) {
                while (r < size) {
                    r = (2 * r + 1);
                    if (f(op(d[r], sm))) {
                        sm = op(d[r], sm);
                        r--;
                    }
                }
                return r + 1 - size;
            }
            sm = op(d[r], sm);
        } while ((r & -r) != r);
        return 0;
    }

  private:
    int _n, size, log;
    std::vector<S> d;

    void update(int k) { d[k] = op(d[2 * k], d[2 * k + 1]); }
};

} // namespace atcoder
using atcoder::segtree;

using S = int;
/*
struct S {
  int min_len;
};
*/
S op(S a, S b) { return min(a, b); }
S e() { return int(1e9); }

template <class T> using mpq = priority_queue<T, vector<T>, greater<T>>;
using ll = long long;
using pii = pair<int, int>;
using piii = pair<pii, int>;

int n, m;
pii arr[500003];
pii seg[500003];
piii q[500003];

int main(int argc, char **argv)
{
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; ++i)
        scanf("%d", &arr[i].first), arr[i].second = i;
    sort(arr + 1, arr + 1 + n);

    int scnt = 0;
    for (int i = 1; i <= n; ++i)
        if (arr[i].first == arr[i + 1].first)
            seg[scnt].first = arr[i + 1].second, seg[scnt].second = arr[i].second, scnt += 1;
    sort(seg, seg + scnt);

    for (int i = 1; i <= m; ++i) {
        scanf("%d%d", &q[i].first.second, &q[i].first.first);
        q[i].second = i;
    }
    sort(q + 1, q + 1 + m);
    segtree<S, op, e> st(500003);
    vector<int> ans(m + 1);
    for (int i = 1, sid = 0; i <= m; ++i) {
        while (seg[sid].first <= q[i].first.first) {
            int l = seg[sid].second;
            int len = seg[sid].first - seg[sid].second;
            st.set(l, len);
            ++sid;
        }
        int res = st.prod(q[i].first.second, q[i].first.first + 1);
        ans[q[i].second] = (res == e() ? -1 : res);
    }
    for (int i = 1; i < ans.size(); ++i)
        printf("%d\n", ans[i]);
    return 0;
};