Language: C++

# include "bits/stdc++.h"
using namespace std;
using LL = long long;
using ULL = unsigned long long;
const double PI = acos(-1);
template<class T>constexpr T INF() { return ::std::numeric_limits<T>::max(); }
template<class T>constexpr T HINF() { return INF<T>() / 2; }
template <typename T_char>T_char TL(T_char cX) { return tolower(cX); };
template <typename T_char>T_char TU(T_char cX) { return toupper(cX); };
const int vy[] = { -1, -1, -1, 0, 1, 1, 1, 0 }, vx[] = { -1, 0, 1, 1, 1, 0, -1, -1 };
const int dx[4] = { -1,0,1,0 }, dy[4] = { 0,-1,0,1 };
const char dir[4] = { 'u','l','d','r' };
int popcnt(unsigned long long n) { int cnt = 0; for (int i = 0; i < 64; i++)if ((n >> i) & 1)cnt++; return cnt; }
int d_sum(LL n) { int ret = 0; while (n > 0) { ret += n % 10; n /= 10; }return ret; }
int d_cnt(LL n) { int ret = 0; while (n > 0) { ret++; n /= 10; }return ret; }
LL gcd(LL a, LL b) { if (b == 0)return a; return gcd(b, a%b); };
LL lcm(LL a, LL b) { LL g = gcd(a, b); return a / g*b; };
# define ALL(qpqpq)           (qpqpq).begin(),(qpqpq).end()
# define UNIQUE(wpwpw)        sort(ALL((wpwpw)));(wpwpw).erase(unique(ALL((wpwpw))),(wpwpw).end())
# define LOWER(epepe)         transform(ALL((epepe)),(epepe).begin(),TL<char>)
# define UPPER(rprpr)         transform(ALL((rprpr)),(rprpr).begin(),TU<char>)
# define FOR(i,tptpt,ypypy)   for(LL i=(tptpt);i<(ypypy);i++)
# define REP(i,upupu)         FOR(i,0,upupu)
# define INIT                 std::ios::sync_with_stdio(false);std::cin.tie(0)
# pragma warning(disable:4996)

int n, m;
int a[101010];
int b[101010];
vector<pair<LL, LL>> c;

struct BIT {
	vector<LL> bit;
	BIT(LL n) {
		bit.resize(n + 10);
		for (int i = 0; i < n + 10; i++)bit[i] = 0;
	}
	//[0,i)
	LL sum(int i) {
		LL s = 0;
		for (int x = i - 1; x >= 0; x = (x&(x + 1)) - 1) {
			(s += bit[x])%mod;
		}
		return s;
	}
	void add(int a, LL w) {
		for (int x = a; x < bit.size(); x |= x + 1) {
			(bit[x] += w) % mod;
		}
	}
};
const int mod = 1e9 + 7;

bool calc(pair<LL, LL> p, pair<LL, LL> q) {
	if (p.first == q.first)return p.second > q.second;
	return p < q;
}

int main() {
	cin >> n >> m;
	REP(i, n)cin >> a[i];
	REP(i, m)cin >> b[i];
	REP(i, n) {
		int it = lower_bound(b, b + m, a[i]) - b;
		if (it == 0 || it == m)continue;
		c.emplace_back(make_pair(a[i] - b[it - 1], b[it] - a[i]));
	}
	sort(ALL(c));
	UNIQUE(c);
	sort(ALL(c), calc);
	vector<LL> d;
	int N = c.size(), id = 1;
	REP(i, N)d.emplace_back(c[i].second);
	sort(ALL(d));
	UNIQUE(d);
	map<LL, LL>mp;
	REP(i, d.size()) {
		if (mp.find(d[i]) == mp.end()) {
			mp[d[i]] = id;
			id++;
		}
	}
	REP(i, N)c[i].second = mp[c[i].second];
	BIT bit(n);
	bit.add(0, 1);
	LL ans = 1;
	REP(i, N) {
		LL t = bit.sum(c[i].second);
		bit.add(c[i].second, t);
		ans += t;
		ans %= mod;
	}
	cout << ans%mod << endl;
}

Compiler output:
a.cc: In member function 'LL BIT::sum(int)':
a.cc:42:39: error: 'mod' was not declared in this scope; did you mean 'modf'?
   42 |                         (s += bit[x])%mod;
      |                                       ^~~
      |                                       modf
a.cc: In member function 'void BIT::add(int, LL)':
a.cc:48:41: error: 'mod' was not declared in this scope; did you mean 'modf'?
   48 |                         (bit[x] += w) % mod;
      |                                         ^~~
      |                                         modf