#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;
using Graph = vector<vector<int>>;
const long long INF = 1LL << 60;
const int INT_INF = 1000000000;
int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const int mod = 1000000007;
struct mint {
  ll x;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint &operator-=(const mint a) {
    if ((x += mod - a.x) >= mod) x -= mod;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const { return mint(*this) += a; }
  mint operator-(const mint a) const { return mint(*this) -= a; }
  mint operator*(const mint a) const { return mint(*this) *= a; }
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1) a *= *this;
    return a;
  }
  mint inv() const { return pow(mod - 2); }
  mint &operator/=(const mint a) { return *this *= a.inv(); }
  mint operator/(const mint a) const { return mint(*this) /= a; }
};
istream &operator>>(istream &is, const mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }
struct combination {
  vector<mint> fact, ifact;
  combination(int n) : fact(n + 1), ifact(n + 1) {
    assert(n < mod);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i) fact[i] = fact[i - 1] * i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i) ifact[i - 1] = ifact[i] * i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n) return 0;
    return fact[n] * ifact[k] * ifact[n - k];
  }
  mint p(int n, int k) { return fact[n] * ifact[n - k]; }
} c(1000005);
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int N, K;
  cin >> N >> K;
  vector<P> v(K);
  for (auto &it : v) cin >> it.first >> it.second;
  vector<mint> dp(N, 0), sdp(N + 1, 0);
  dp[0] = 1, sdp[1] = 1;
  for (int n = 1; n < N; n++) {
    for (auto p : v) {
      int left = max(0, n - p.second);
      int right = max(0, n - p.first + 1);
      dp[n] += sdp[right] - sdp[left];
    }
    sdp[n + 1] = sdp[n] + dp[n];
  }
  cout << dp[N - 1] << endl;
  return 0;
}
