#include <bits/stdc++.h>
#define REP(i, s, n) for (int i = s; i < (int)(n); i++)
#define ALL(a) a.begin(), a.end()
#define MOD 1000000007
using namespace std;
using ll = long long;

template<int M>
class ModInt {
   public:
    ll value;
    constexpr ModInt(ll v = 0) { value = v % M; if (value < 0) value += M; }
    constexpr ModInt pow(ll n) const { if (!n) return 1; ModInt a = pow(n >> 1); a *= a; if (n & 1) a *= *this; return a; }
    constexpr ModInt inv() const { return this->pow(M - 2); }
    constexpr ModInt operator + (const ModInt &rhs) const { return ModInt(*this) += rhs; };
    constexpr ModInt operator - (const ModInt &rhs) const { return ModInt(*this) -= rhs; };
    constexpr ModInt operator * (const ModInt &rhs) const { return ModInt(*this) *= rhs; };
    constexpr ModInt operator / (const ModInt &rhs) const { return ModInt(*this) /= rhs; };
    constexpr ModInt &operator += (const ModInt &rhs) { value += rhs.value; if (value >= M) value -= M; return *this; };
    constexpr ModInt &operator -= (const ModInt &rhs) { value -= rhs.value; if (value <  0) value += M; return *this; };
    constexpr ModInt &operator *= (const ModInt &rhs) { value = value * rhs.value % M; return *this; };
    constexpr ModInt &operator /= (const ModInt &rhs) { return (*this) *= rhs.inv(); };
    constexpr bool operator == (const ModInt &rhs) { return value == rhs.value; }
    constexpr bool operator != (const ModInt &rhs) { return value != rhs.value; }
    friend ostream &operator << (ostream &os, const ModInt &rhs) { os << rhs.value; return os; }
};

using mint = ModInt<MOD>;

int main() {
    int N, M; cin >> N >> M;
    vector<int> A(N); REP(i, 0, N) cin >> A[i];

    ll S = accumulate(ALL(A), 0LL);
    mint ans = 1;
    REP(i, 0, N + S) {
        ans *= (N + M - i);
        ans /= (N + S - i);
    }
    cout << ans << endl;
    
    return 0;
}
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using uint = unsigned int;
using ull = unsigned long long;
#define rep(i,n) for(int i=0;i<int(n);i++)
#define rep1(i,n) for(int i=1;i<=int(n);i++)
#define per(i,n) for(int i=int(n)-1;i>=0;i--)
#define per1(i,n) for(int i=int(n);i>0;i--)
#define all(c) c.begin(),c.end()
#define si(x) int(x.size())
#define pb emplace_back
#define fs first
#define sc second
template<class T> using V = vector<T>;
template<class T> using VV = vector<vector<T>>;
template<class T,class U> void chmax(T& x, U y){if(x<y) x=y;}
template<class T,class U> void chmin(T& x, U y){if(y<x) x=y;}
template<class T> void mkuni(V<T>& v){sort(all(v));v.erase(unique(all(v)),v.end());}
template<class T> int lwb(const V<T>& v, const T& a){return lower_bound(all(v),a) - v.begin();}
template<class S,class T> ostream& operator<<(ostream& o,const pair<S,T> &p){
	return o<<"("<<p.fs<<","<<p.sc<<")";
}
template<class T> ostream& operator<<(ostream& o,const vector<T> &vc){
	o<<"{";
	for(const T& v:vc) o<<v<<",";
	o<<"}";
	return o;
}
constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n-1); }

#ifdef LOCAL
#define show(x) cerr << "LINE" << __LINE__ << " : " << #x << " = " << (x) << endl
void dmpr(ostream& os){os<<endl;}
template<class T,class... Args>
void dmpr(ostream&os,const T&t,const Args&... args){
	os<<t<<" ~ ";
	dmpr(os,args...);
}
#define shows(...) cerr << "LINE" << __LINE__ << " : ";dmpr(cerr,##__VA_ARGS__)
#define dump(x) cerr << "LINE" << __LINE__ << " : " << #x << " = {";  \
	for(auto v: x) cerr << v << ","; cerr << "}" << endl;
#else
#define show(x) void(0)
#define dump(x) void(0)
#define shows(...) void(0)
#endif

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);		//DON'T USE scanf/printf/puts !!
	cout << fixed << setprecision(20);

	int N;
	double D,H;
	cin >> N >> D >> H;
	double ans = 0;
	while(N--){
		double d,h; cin >> d >> h;
		chmax(ans,h-(H-h)/(D-d)*d);
	}
	cout << ans << endl;
}
