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M.cpp
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M.cpp
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//#pragma GCC optimize "trapv"
#include<bits/stdc++.h>
#define ll long long int
#define fab(a,b,i) for(int i=a;i<b;i++)
#define pb push_back
#define db double
#define mp make_pair
#define endl "\n"
#define f first
#define se second
#define all(x) x.begin(),x.end()
#define MOD 1000000007
#define quick ios_base::sync_with_stdio(false);cin.tie(NULL)
using namespace std;
ll dp[105][100005],n,k,a[105];
int main()
{ quick;
cin>>n>>k;
fab(0,n,i)
cin>>a[i];
ll pref[k+1]={0};
dp[0][0]=1;
pref[0]=1;
fab(1,a[0]+1,i)
{
dp[0][i]=1;
//pref[i]=pref[i-1]+dp[0][i];
}
fab(1,k+1,i)
pref[i]=(pref[i-1]+dp[0][i])%MOD;
fab(0,n,i)
dp[i][0]=1;
fab(1,n,i)
{
fab(1,k+1,j)
{
ll tot=max((ll)(0),j-a[i]),op;
if(tot==0)
op=(pref[j])%MOD;
else
op=(pref[j]-pref[tot-1])%MOD;
//assert(op>=0);
op=op+MOD;
dp[i][j]=(op)%MOD;//+(tot==0?j:a[i]);
}
//cout<<pref[0]<<" ";
fab(1,k+1,j)
{
//cout<<pref[j]<<" ";
pref[j]=(pref[j-1]%MOD+dp[i][j])%MOD;
}
//cout<<endl;
}
//cout<<"\n\n";
/*fab(0,n,i)
{fab(0,k+1,j)
cout<<dp[i][j]<<" ";
cout<<endl;}*/
cout<<dp[n-1][k]%MOD;
return 0;
}