Coin Combinations I - C++

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;typedef long double llf;typedef double fl;typedef string str;typedef pair<double, double> dd;
typedef vector<int> vi;typedef vector<vector<int>> vvi;typedef vector<fl> vf;typedef vector<ll> vl;
typedef vector<llf> vlf;typedef vector<char> vc;typedef vector<str> vs;typedef pair<int,int> ii;
# define f(i,a,b,c) for(ll i=a;i<b;i+=c)
# define fd(i,a,b,c) for(ll i=a;i>=b;i-=c)
# define w(x) while(x--)
# define ctoi(a) (a-'0')
# define pb push_back
# define eb emplace_back
# define lb lower_bound
# define ub upper_bound
# define be(x) x.begin(), x.end()
# define rbe(x) x.rbegin(), x.rend()
# define _(x) ios::sync_with_stdio(0);cin.tie(0);cout.precision(x);cout.setf(ios::fixed);

const int MOD = 1e9+7, MAX = 100000010;
ll n, m, coins[100], memo[MAX], confirm[MAX];
ll dp(ll x){
    if(x<0)return 0;
    if(x==0)return 1;
    if(confirm[x])return memo[x]%MOD;
    confirm[x]=1;
    ll sum_coins=0;
    f(i,0,n,1)sum_coins+=dp(x-coins[i]);
    return memo[x]=sum_coins;
}
int main(){_(0)
    cin>>n>>m;
    f(i,0,n,1)cin>>coins[i];
    cout<<dp(m)%MOD<<'\n';
return 0;}