CSES - Shared codeLink to this code: https://cses.fi/paste/06074e54d99c3bb248646e/
#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
#define IOS ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
typedef pair<int,int>pr;
#define all(i) i.begin() , i.end()
#define ft first
#define sn second
#define pb push_back
const int mod = 1e9+7;
#define en "\n"
#define dbg cout<<"rony\n";
#define MAXN 3000010
ll fact[MAXN];
ll Bigmod(ll a,ll n)
{
ll rs = 1;
while(n)
{
if(n%2 == 0){
n /= 2;
a = (a * a)%mod;
}
else{
n--;
rs = (rs * a)%mod;
}
}
return rs;
}
ll nCr(ll n,ll r)
{
fact[0] = 1;
for(int i = 1;i <= n;i++)
{
fact[i] = fact[i-1] * i;
fact[i] %= mod;
}
ll an = fact[n];
an = an * (Bigmod(fact[r],mod - 2));
an %= mod;
an = an * (Bigmod(fact[n - r],mod - 2));
an %= mod;
return an;
}
void solve()
{
int n,m;
cin >> n >> m;
int r = m;
if(n-1 <= m)
r = n-1;
cout<<nCr(n + m - 1, r)<<en;
}
int main()
{
IOS;
int t;
// cin >> t;
t = 1;
while ( t-- )
{
solve();
}
return 0;
}