#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }
#define COLOR(s) ("\x1b[" s "m")


// floor(a / b)
Int divFloor(Int a, Int b) {
  return a / b - (((a ^ b) < 0 && a % b != 0) ? 1 : 0);
}

// ceil(a / b)
Int divCeil(Int a, Int b) {
  return a / b + (((a ^ b) > 0 && a % b != 0) ? 1 : 0);
}


// point add, rectangle sum
template <class X, class Y, class T> struct Bit2d {
  vector<X> xs;
  vector<pair<Y, X>> yxs;
  vector<vector<Y>> yss;
  int m;
  vector<int> ns;
  vector<vector<T>> bit;
  Bit2d() {}
  void book(X x, Y y) {
    xs.push_back(x);
    yxs.emplace_back(y, x);
  }
  void build() {
    sort(xs.begin(), xs.end());
    xs.erase(unique(xs.begin(), xs.end()), xs.end());
    m = xs.size();
    yss.assign(m, {});
    sort(yxs.begin(), yxs.end());
    for (const auto &yx : yxs) {
      const X x = yx.second;
      const Y y = yx.first;
      const int a = lower_bound(xs.begin(), xs.end(), x) - xs.begin();
      assert(a < m); assert(xs[a] == x);
      for (int u = a; u < m; u |= u + 1) yss[u].push_back(y);
    }
    ns.assign(m, 0);
    bit.assign(m, {});
    for (int u = 0; u < m; ++u) {
      yss[u].erase(unique(yss[u].begin(), yss[u].end()), yss[u].end());
      ns[u] = yss[u].size();
      bit[u].assign(ns[u], 0);
    }
  }
  void add(X x, Y y, T val) {
    const int a = lower_bound(xs.begin(), xs.end(), x) - xs.begin();
    assert(a < m); assert(xs[a] == x);
    for (int u = a; u < m; u |= u + 1) {
      const int b = lower_bound(yss[u].begin(), yss[u].end(), y) - yss[u].begin();
      assert(b < ns[u]); assert(yss[u][b] == y);
      for (int v = b; v < ns[u]; v |= v + 1) bit[u][v] += val;
    }
  }
  T get(X x0, X x1, Y y0, Y y1) const {
    const int a0 = lower_bound(xs.begin(), xs.end(), x0) - xs.begin();
    const int a1 = lower_bound(xs.begin(), xs.end(), x1) - xs.begin();
    T ret = 0;
    for (int u = a0; u; u &= u - 1) ret -= get(u - 1, y0, y1);
    for (int u = a1; u; u &= u - 1) ret += get(u - 1, y0, y1);
    return ret;
  }
 private:
  T get(int u, Y y0, Y y1) const {
    T ret = 0;
    const int b0 = lower_bound(yss[u].begin(), yss[u].end(), y0) - yss[u].begin();
    const int b1 = lower_bound(yss[u].begin(), yss[u].end(), y1) - yss[u].begin();
    for (int v = b0; v; v &= v - 1) ret -= bit[u][v - 1];
    for (int v = b1; v; v &= v - 1) ret += bit[u][v - 1];
    return ret;
  }
};


int N, Q;
vector<Int> A;
vector<int> P;
vector<Int> V;

Int M;
vector<Int> B;


namespace brute {
Int solve(vector<Int> bs) {
  vector<Int> qs(N), rs(N);
  for (int i = 0; i < N; ++i) {
    qs[i] = divFloor(bs[i], M);
    rs[i] = bs[i] - M * qs[i];
  }
  Int ans = 0;
  for (int i = 0; i < N; ++i) for (int j = i + 1; j < N; ++j) {
    if (rs[i] == rs[j]) {
      return -1;
    }
    ans += abs(qs[j] - qs[i] - ((rs[i] > rs[j]) ? 1 : 0));
  }
  return ans;
}
vector<Int> run() {
cerr<<"[brute::run]"<<endl;
  vector<Int> ans(Q, -1);
  auto bs = B;
  for (int q = 0; q < Q; ++q) {
    bs[P[q]] += V[q];
// cerr<<COLOR("33")<<bs<<COLOR()<<endl;
    ans[q] = solve(bs);
    bs[P[q]] -= V[q];
  }
  return ans;
}
}  // brute


namespace brute2 {
Int solve(vector<Int> bs) {
  vector<Int> qs(N), rs(N);
  for (int i = 0; i < N; ++i) {
    qs[i] = divFloor(bs[i], M);
    rs[i] = bs[i] - M * qs[i];
  }
  for (int i = 0; i < N; ++i) for (int j = i + 1; j < N; ++j) {
    if (rs[i] == rs[j]) {
      return -1;
    }
  }
  Int ans = 0;
  for (int i = 0; i < N; ++i) for (int j = i + 1; j < N; ++j) {
    ans += abs(qs[j] - qs[i]);
  }
  for (int i = 0; i < N; ++i) for (int j = i + 1; j < N; ++j) {
    if (rs[i] > rs[j]) {
      ans += (1 - 2 * ((qs[i] < qs[j]) ? 1 : 0));
    }
  }
  return ans;
}
vector<Int> run() {
cerr<<"[brute2::run]"<<endl;
  vector<Int> ans(Q, -1);
  auto bs = B;
  for (int q = 0; q < Q; ++q) {
    bs[P[q]] += V[q];
// cerr<<COLOR("33")<<bs<<COLOR()<<endl;
    ans[q] = solve(bs);
    bs[P[q]] -= V[q];
  }
  return ans;
}
}  // brute2


namespace fast {
vector<Int> run() {
cerr<<"[fast::run]"<<endl;
  vector<Int> C(N), D(N);
  for (int i = 0; i < N; ++i) {
    C[i] = divFloor(B[i], M);
    D[i] = B[i] - M * C[i];
  }
  vector<Int> X(Q), Y(Q);
  for (int q = 0; q < Q; ++q) {
    const Int b = B[P[q]] + V[q];
    X[q] = divFloor(b, M);
    Y[q] = b - M * X[q];
  }
/*
cerr<<"C = "<<C<<endl;
cerr<<"D = "<<D<<endl;
cerr<<"P = "<<P<<endl;
cerr<<"X = "<<X<<endl;
cerr<<"Y = "<<Y<<endl;
*/
  
  vector<Int> ans(Q, 0);
  // [i < j] |qs[j] - qs[i]|
  {
    vector<pair<Int, int>> cis(N);
    for (int i = 0; i < N; ++i) cis[i] = make_pair(C[i], i);
    sort(cis.begin(), cis.end());
    vector<Int> sums(N + 1, 0);
    for (int j = 0; j < N; ++j) sums[j + 1] = sums[j] + cis[j].first;
    Int base = 0;
    vector<Int> contris(N, 0);
    for (int j = 0; j < N; ++j) {
      const int i = cis[j].second;
      contris[i] += (j * C[i] - sums[j]);
      contris[i] += ((sums[N] - sums[j + 1]) - (N - (j + 1)) * C[i]);
      base += contris[i];
    }
    assert(base % 2 == 0);
    base /= 2;
// cerr<<"base = "<<base<<", contris = "<<contris<<endl;
    for (int q = 0; q < Q; ++q) {
      const int i = P[q];
      const int j = lower_bound(cis.begin(), cis.end(), make_pair(X[q], -1)) - cis.begin();
      ans[q] += base;
      ans[q] -= contris[i];
      ans[q] += (j * X[q] - sums[j]);
      ans[q] += ((sums[N] - sums[j]) - (N - j) * X[q]);
      ans[q] -= abs(X[q] - C[i]);
    }
  }
  // [i < j] [rs[i] > rs[j]]
  // [i < j] [rs[i] > rs[j]] [qs[i] < qs[j]] 2
  {
    vector<vector<int>> qss(N);
    for (int q = 0; q < Q; ++q) qss[P[q]].push_back(q);
    Int base = 0;
    vector<Int> contris(N, 0);
    Bit2d<Int, Int, Int> bit2d;
    for (int i = 0; i < N; ++i) bit2d.book(C[i], D[i]);
    bit2d.build();
    const Int xL = *min_element(C.begin(), C.end());
    const Int xR = *max_element(C.begin(), C.end()) + 1;
    const Int yL = *min_element(D.begin(), D.end());
    const Int yR = *max_element(D.begin(), D.end()) + 1;
    auto getL = [&](Int x, Int y) -> Int {
      const Int res0 = bit2d.get(xL, xR, y + 1, yR);
      const Int res1 = bit2d.get(xL, x, y + 1, yR);
      return res0 - 2 * res1;
    };
    auto getR = [&](Int x, Int y) -> Int {
      const Int res0 = bit2d.get(xL, xR, yL, y);
      const Int res1 = bit2d.get(x + 1, xR, yL, y);
      return res0 - 2 * res1;
    };
    for (int i = 0; i < N; ++i) {
      contris[i] += getL(C[i], D[i]);
      base += contris[i];
      for (const int q : qss[i]) ans[q] += getL(X[q], Y[q]);
      bit2d.add(C[i], D[i], +1);
    }
    for (int i = 0; i < N; ++i) {
      bit2d.add(C[i], D[i], -1);
      contris[i] += getR(C[i], D[i]);
      for (const int q : qss[i]) ans[q] += getR(X[q], Y[q]);
    }
    for (int q = 0; q < Q; ++q) {
      const int i = P[q];
      ans[q] += base;
      ans[q] -= contris[i];
    }
  }
  
  vector<int> can(Q, 0);
  {
    map<Int, int> freq;
    int bad = 0;
    auto add = [&](Int d, int sig) -> void {
      bad -= max(freq[d] - 1, 0);
      freq[d] += sig;
      bad += max(freq[d] - 1, 0);
    };
    for (int i = 0; i < N; ++i) {
      add(D[i], +1);
    }
    for (int q = 0; q < Q; ++q) {
      const int i = P[q];
      add(D[i], -1);
      add(Y[q], +1);
      can[q] = (bad == 0);
      add(Y[q], -1);
      add(D[i], +1);
    }
  }
// cerr<<"can = "<<can<<endl;
  for (int q = 0; q < Q; ++q) if (!can[q]) {
    ans[q] = -1;
  }
  return ans;
}
}  // fast


int main() {
  for (; ~scanf("%d%d", &N, &Q); ) {
    A.resize(N);
    for (int i = 0; i < N; ++i) {
      scanf("%lld", &A[i]);
      if (i & 1) A[i] *= -1;
    }
    P.resize(Q);
    V.resize(Q);
    for (int q = 0; q < Q; ++q) {
      scanf("%d%lld", &P[q], &V[q]);
      if (P[q] & 1) V[q] *= -1;
      ++P[q] %= N;
    }
    
    B.assign(N + 1, 0);
    for (int i = 0; i < N; ++i) {
      B[i + 1] = B[i] + A[i];
    }
    M = B[N];
    B.pop_back();
    if (M < 0) {
      M *= -1;
      for (int i = 0; i < N; ++i) {
        B[i] *= -1;
      }
      for (int q = 0; q < Q; ++q) {
        V[q] *= -1;
      }
    }
cerr<<"M = "<<M<<endl;
    
    vector<Int> ans(Q, -1);
    if (N % 2 == 0 && M > 0) {
      ans = fast::run();
    }
    for (int q = 0; q < Q; ++q) {
      printf("%lld\n", ans[q]);
    }
  }
  return 0;
}