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  Runtime error ：

#include<bits/stdc++.h> 

using namespace std;

const int mod = 1e9+7;

vector<vector<long long int>> res;
vector<long long int> arr2;
long long int target;
long long int start,last=0;
vector<long long int> temp;
long long int tim=0;

int OK(vector<long long int>a,long long int k,long long int i)// Determine whether there are duplicate elements 
{
    if(i>k)// Ensure that the array exists 
    for(int t=k;t<i;t++)// Loop search 
    {
        if(a[t]==a[i])
        return 0;
    }
        return 1;
}

void Perm(vector<long long int>a,long long int k,long long int m)// Full Permutation implementation function 
{
    if(k==m)// only 1 Elements 
    {
        tim++;// frequency +1
//        for(int i=0;i<=m;i++)
//        {
//            cout<<a[i];
//        }
//        cout<<"\n";
    }
    else  // There are more elements to arrange 
    {
        for(int i=k;i<=m;i++)// There are a few elements that cycle several times （ Because it starts , Then arrange the following numbers completely ）
        {
            if(OK(a,k,i))// When there is no repeating element , Before full arrangement 
            {
                swap(a[k],a[i]);// swapping 
                Perm(a,k+1,m);
                swap(a[k],a[i]);
            }
        }
    }
}

int helper(vector<long long int> arr, long long int target, vector<long long int> arr2, long long int index){
	if(target==0)
	{
		res.insert(res.end(),arr2);
	}
	
	for(int i=index; i<arr.size();i++){
		if(arr[i] <= target){
			arr2.insert(arr2.end(),arr[i]);
			helper(arr, target-arr[i], arr2, i);
			arr2.pop_back();
		}
	}
}

vector<vector<long long int>> combinationSum(vector<long long int> arr, long long int target){
	helper(arr, target, arr2, 0);
	return res;
} 

int main()
{
    vector<long long int> arr;  // The original array  
   	long long int n,m,k,x;  
    cin >> x >> n >> m >> k;

	target = x;
    arr.insert(arr.end(),n);
    arr.insert(arr.end(),m);
    arr.insert(arr.end(),k);

    combinationSum(arr,target);
    
    for(int i=0;i<res.size();i++){ 
    	for(int j=0;j<res[i].size();j++){
    		start = 0; 		
    		temp.insert(temp.end(), res[i][j]);
		}

		last = res[i].size()-1;
		Perm(temp, start, last);
		temp.clear();
	}
    
    if(tim){
        cout << tim%mod;
    }
    else{
        cout << "impossible";
    }

//	cout << " The number of components is ：" << tim ; 
    return 0;
}