Language: C++

#include <bits/stdc++.h>
#define endl '\n'
#define ALL(v) std::begin(v), std::end(v)
#define ALLR(v) std::rbegin(v), std::rend(v)
using ll = std::int64_t;
using ull = std::uint64_t;
using pll = std::pair<ll, ll>;
using tll = std::tuple<ll, ll, ll>;
template <typename T> using vec = std::vector<T>;
template <typename T> using vvec = vec<vec<T>>;
template <typename T> const T& var_min(const T &t) { return t; }
template <typename T> const T& var_max(const T &t) { return t; }
template <typename T, typename... Tail> const T& var_min(const T &t, const Tail&... tail) { return std::min(t, var_min(tail...)); }
template <typename T, typename... Tail> const T& var_max(const T &t, const Tail&... tail) { return std::max(t, var_max(tail...)); }
template <typename T, typename... Tail> void chmin(T &t, const Tail&... tail) { t = var_min(t, tail...); }
template <typename T, typename... Tail> void chmax(T &t, const Tail&... tail) { t = var_max(t, tail...); }
template <typename T> const T& clamp(const T &t, const T &low, const T &high) { return std::max(low, std::min(high, t)); }
template <typename T> void chclamp(T &t, const T &low, const T &high) { return t = clamp(t, low, high); }
namespace init__ { struct InitIO { InitIO() { std::cin.tie(nullptr); std::ios_base::sync_with_stdio(false); std::cout << std::fixed << std::setprecision(30); } } init_io; }
#define mv_rec make_v(init, tail...)
template <typename T> T make_v(T init) { return init; }
template <typename T, typename... Tail> auto make_v(T init, size_t s, Tail... tail) { return vec<decltype(mv_rec)>(s, mv_rec); }
#undef mv_rec


namespace math {

template <typename T>
constexpr T pow(const T &n, ll k) {
    T ret = n.mul_id_ele();
    T cur = n;
    while (k) {
        if (k & 1) ret *= cur;
        cur *= cur;
        k /= 2;
    }
    return ret;
}

}

namespace math {

template <ll Mod>
struct Modint {

    constexpr Modint(ll x) : x(x % Mod) { }
    
    constexpr Modint() : Modint(0) { }
    
    constexpr Modint<Mod> add_id_ele() const { 
        return Modint<Mod>(0); 
    }
    
    constexpr Modint<Mod> mul_id_ele() const {
        return Modint<Mod>(1); 
    }
    
    constexpr ll& value() { 
        return x; 
    }
    
    constexpr ll value() const {
        return x; 
    }

    constexpr Modint& operator +=(const Modint &oth) {
        x += oth.value();
        if (Mod <= x) x -= Mod;
        return *this;
    }

    constexpr Modint& operator -=(const Modint &oth) {
        x += Mod - oth.value();
        if (Mod <= x) x -= Mod;
        return *this;
    }

    constexpr Modint& operator *=(const Modint &oth) {
        x *= oth.value();
        x %= Mod;
        return *this;
    }

    constexpr Modint& operator /=(const Modint &oth) {
        x *= oth.inv();
        x %= Mod;
        return *this;
    }

    constexpr Modint operator +(const Modint &oth) const {
        return Modint(x) += oth;
    }

    constexpr Modint operator -(const Modint &oth) const {
        return Modint(x) -= oth;
    }

    constexpr Modint operator *(const Modint &oth) const {
        return Modint(x) *= oth;
    }

    constexpr Modint operator /(const Modint &oth) const {
        return Modint(x) /= oth;
    }

    constexpr Modint operator -() const {
        return Modint((x != 0) * (Mod - x)); 
    }

    template <typename T>
    constexpr typename std::enable_if<std::is_integral<T>::value, const Modint&>::type
    operator =(T t) {
        (*this) = Modint(std::forward<T>(t)); 
        return *this;
    }

    constexpr Modint inv() const {
        return ::math::pow(*this, Mod - 2);
    }

    constexpr ll mod() const {
        return Mod;
    }

private:
    ll x;
};

}

const ll mod = 1e9 + 7;
const ll inf = 5e15;
using mint = math::Modint<mod>;
const std::size_t SIZE = 3010;
mint dp_buf[2][SIZE];
auto dp1 = dp_buf[0], dp2 = dp_buf[1];

int main() {
    ll n, m;
    std::string s;
    std::cin >> n >> m >> s;
    vec<ll> rights(n, -inf);
    for (ll i = 0; i < m; i++) {
        ll l, r;
        std::cin >> l >> r;
        chmax(rights[l - 1], r);
    }

    {
        ll maxr = -inf;
        for (ll i = 0; i < n; i++) {
            if (rights[i] <= maxr) rights[i] = -inf;
            else maxr = rights[i];
        }
    }

    std::queue<pll> ops;
    for (ll i = 0; i < n; i++) if (rights[i] != -inf) ops.emplace(i, rights[i]);

    vec<ll> sum(n + 1);
    for (ll i = 0; i < n; i++) sum[i + 1] = sum[i] + (s[i] == '1');

    auto calc_dp = [&](std::queue<pll> &ranges) {
        ll minl, cr;
        std::tie(minl, cr) = ranges.front();
        ranges.pop();
        std::fill(dp1, dp1 + SIZE, mint(0));
        dp1[0] = 1;
        for (ll i = minl;; i++) {
            if (ranges.empty() && i == cr) break;
            std::fill(dp2, dp2 + SIZE, mint(0));
            if (ranges.size() && ranges.front().first == i) {
                cr = ranges.front().second;
                ranges.pop();
            }
            for (ll j = 0; j <= sum[cr] - sum[minl]; j++) {
                if (j < sum[cr] - sum[minl]) dp2[j + 1] += dp1[j];
                if (sum[cr] - sum[minl] <= j + (cr - i) - 1) dp2[j] += dp1[j];
            }
            std::copy(dp2, dp2 + SIZE, dp1);
        }

        return dp1[sum[cr] - sum[minl]];
    };

    mint ans = 1;
    while (ops.size()) {
        std::queue<pll> que;
        auto move_ele = [&] {
            que.push(ops.front());
            ops.pop();
        };

        move_ele();
        ll cr = que.front().second;
        while (ops.size()) {
            ll l, r;
            std::tie(l, r) = ops.front();
            if (cr <= l) break;
            cr = r;
            move_ele();
        }

        vec<pll> tmp;
        auto cpy = que;
        while (cpy.size()) { tmp.push_back(cpy.front()); cpy.pop(); }
#endif
        ans *= calc_dp(que);
    }

    std::cout << ans.value() << endl;
    return 0;
}


Compiler output:
a.cc:208:2: error: #endif without #if
  208 | #endif
      |  ^~~~~