// tsutaj's solution
// Expected Status: Accepted

#include <cstdio>
#include <algorithm>
int a[310], dp[45000];
const int MOD = 1000000007;
int main() {
    int N, K; scanf("%d%d", &N, &K);
    for(int i=0; i<N; i++) {
        scanf("%d", &a[i]);
    }

    for(int i=0; i<=K; i++) dp[i] = 1;
    for(int i=0; i<N; i++) {
        for(int j=K; j>=0; j--) {
            int lb = j-i-1, ub = j;
            if(lb < 0) (dp[j] = dp[ub]) %= MOD;
            else (dp[j] = (dp[ub] - dp[lb] + MOD)) %= MOD;
        }
        for(int j=1; j<=K; j++) {
            (dp[j] += dp[j-1]) %= MOD;            
        }
    }

    int ans = dp[K];
    printf("%d\n", ans);
    return 0;
}