#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long int lli;
#define ff              first
#define ss              second
#define pb              push_back
#define mp              make_pair
#define pii             pair<lli,lli>
#define vi              vector<lli>
#define mii             map<lli,lli>
#define pqb             priority_queue<lli>
#define pqs             priority_queue<lli,vi,greater<lli> >
#define setbits(x)      __builtin_popcountll(x)
#define zrobits(x)      __builtin_ctzll(x)
#define mod             1000000007
#define inf             1e18
#define ps(x,y)         fixed<<setprecision(y)<<x
#define mk(arr,n,type)  type *arr=new type[n];
#define w(x)            lli x; cin>>x; while(x--)
mt19937                 rng(chrono::steady_clock::now().time_since_epoch().count());
#define ONLINE_JUDGE
typedef tree<lli, null_type, less<lli>, rb_tree_tag, tree_order_statistics_node_update> pbds;


void zanj0()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
}
lli b, g, n1, n2;
lli x, y;
lli n;
lli add(lli a, lli b) {
    return ((a % mod) + (b % mod)) % mod;
}
lli help(lli b, lli g, lli n1, lli n2, vector < vector < vector < vector <lli> > > >& dp) {
    if (b == g && b == 0) return 1;
    if (dp[b][g][n1][n2] != -1) return dp[b][g][n1][n2];
    lli ret = 0;
    if (b > 0 && n1 > 0) {
        ret = add(ret, help(b - 1, g, n1 - 1, y, dp));
    }
    if (g > 0 && n2 > 0) {
        ret = add(ret, help(b, g - 1, x, n2 - 1, dp));
    }
    return dp[b][g][n1][n2] = ret;
}
void solve() {

    cin >> b >> g >> n1 >> n2;
    x = n1;
    y = n2;
    n = b + g;
    vector < vector < vector < vector <lli> > > > dp(b + 1, vector < vector < vector <lli> > >(g + 1, vector < vector < lli > >(n1 + 1, vector <lli> (n2 + 1, -1))));
    cout << help(b, g, n1, n2, dp) << endl;
}
int main()
{
    zanj0();
    solve();
    return 0;
}