c++ for coin combination problem not working

Question

I am solving the coin combination problem given below:

Consider a money system consisting of n coins. Each coin has a positive integer value. Your task is to calculate the number of distinct ordered ways you can produce a money sum x using the available coins.

For example, if the coins are {2,3,5} and the desired sum is 9, there are 3 ways:

• 2+2+5
• 3+3+3
• 2+2+2+3

Input:

The first input line has two integers n and x: the number of coins and the desired sum of money.

The second line has n distinct integers c1,c2,…,cn: the value of each coin.

Output:

Print one integer: the number of ways modulo 109+7.

For more information here is the link to the given problem: https://cses.fi/problemset/task/1636

I tried writing the following code in C++ using dynamic programming:

#include<bits/stdc++.h>
using namespace std;
 
const long N=1e6+10,mod=1e9+7;
long dp[N];
 
long recursion(int coins,int sum,int a[])
{
    if(sum==0)
        return 1;
    if(dp[sum]!=-1)
        return dp[sum];
    long count=0;
    for(long i=0;i<coins;i++)
    {
        if(sum-a[i]>=0)
            count=count+recursion(coins,sum-a[i],a);
    }
    return dp[sum]=count%mod;
} 
 
int main()
{
    memset(dp,-1,sizeof(dp));
    int n,x;
    cin>>n>>x;
    int a[n];
    for(int i=0;i<n;i++)
    {
        cin>>a[i];
    }
    cout<<recursion(n,x,a);
    return 0;
}

But it shows wrong answer for some test cases. Can someone please help me sort this problem.