#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define ll long long int
#define MOD 1000000007
#define INF 100000000000000 //INF - 1e14
#define vi vector<ll>
#define pb push_back
#define mpl map<ll,ll>
#define ff first
#define ss second
#define pll pair<ll,ll>
#define vpll vector<pair<ll,ll> >
#define fer(i, a, n) for( ll i = a; i <= n; i++)
#define fdr(i, a, n) for( ll i = a; i >= n; i--)
#define invec(n,v) vi v(n); fer(i,0,n-1) cin >> v[i]
#define insvec(n,v) rin(n); vi v(n); fer(i,0,n-1) cin >> v[i]
#define MK2DV(v,row,col,val) vector<vector<ll> > v(row, vector<ll>(col,val))
#define matrix vector<vector<ll> >
#define printpartition cout << "-------------------------------------------------------------" << endl;
#define printmat(mat,row,col) cout << #mat << "::" << endl; fer(i,0,row-1)fer(j,0,col-1)cout << mat[i][j] << " \n"[j == col-1]; printpartition;
using namespace std;
using namespace __gnu_pbds;
#define ordered_set tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update>
void __print(int x) {cout << x;}
void __print(long x) {cout << x;}
void __print(long long x) {cout << x;}
void __print(unsigned x) {cout << x;}
void __print(unsigned long x) {cout << x;}
void __print(unsigned long long x) {cout << x;}
void __print(float x) {cout << x;}
void __print(double x) {cout << x;}
void __print(long double x) {cout << x;}
void __print(char x) {cout << '\'' << x << '\'';}
void __print(const char *x) {cout << '\"' << x << '\"';}
void __print(const string &x) {cout << '\"' << x << '\"';}
void __print(bool x) {cout << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cout << '{'; __print(x.first); cout << ','; __print(x.second); cout << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cout << '{'; for (auto &i : x) cout << (f++ ? "," : ""), __print(i); cout << "}";}
void _print() {cout << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cout << ", "; _print(v...);}
template <typename T> inline void inp(T &any) {cin >> any;} template <typename T, typename... U>inline void inp(T &a, U &...b) {cin >> a; inp(b...);}
#define rin(args...) ll args; inp(args);
#ifndef ONLINE_JUDGE
#define debug(x...) cout << "[" << #x << "] = ["; _print(x)
#define matdeb(mat,row,col) printmat(mat,row,col);
#else
#define debug(x...)
#define matdeb(mat,row,col)
#endif
ll fast_pow(ll base, ll exp, ll M = MOD) { base = base % M; ll result = 1; while (exp > 0) { if (exp % 2 == 1) result = (result * base) % M; base = (base * base) % M; exp = exp / 2; } return result; }
ll modInverse(ll A, ll M = MOD) { return fast_pow(A, M - 2, M); } // only when M is prime
string yes = "Yes", no = "No";

const int N = 100;
const int K = 100000;
const int opti = 2;
ll dp[2][K + 1];
ll pref[2][K + 1];
ll prefv[N];
int main() {
	ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);

	ll test_cases = 1;
	// cin >> test_cases;
	for (ll test_case = 1; test_case <= test_cases; test_case++) {
		// cout << "Case #" << test_case << ": ";
		rin(n, k);
		invec(n, v);
		prefv[0] = v[0];
		fer(i, 1, n - 1) {
			prefv[i] = prefv[i - 1] + v[i];
		}
		pref[0][0] = 1;
		dp[0][0] = 1;
		fer(j, 0, v[0]) {
			dp[0][j] = 1;
			pref[0][j] = j + 1;
		}
		fer(i, v[0] + 1, k) {
			pref[0][i] = (pref[0][i - 1] + dp[0][i]) % MOD;
		}
		bool vis = false;
		fer(i, 1, n - 1) {
			fer(j, 0, k) {
				dp[i & 1][j] = (pref[(i - 1) & 1][j] - pref[(i - 1) & 1][max(0LL, j - v[i])] + dp[(i - 1) & 1][max(0LL, j - v[i])] + MOD) % MOD;
				pref[i & 1][j] = (pref[i & 1][max(0LL, j - 1)] + dp[i & 1][j]) % MOD;
			}
		}
		cout << dp[(n - 1) & 1][k];
		// debug(n - 1, k);
		// debug(dp[n - 1][k]);
		// matdeb(pref, n, k + 1);
		// matdeb(dp, n, k + 1);
	}
	return 0;
}

Measured memory_bytes: 3328