#include <iostream>
#include <vector>
#include <cstring>
using namespace std;
typedef long long ll;
const int maxn = 105;
int food,  rooms, max_cap;

ll dp[maxn][maxn];
ll rec(int at_food, int room_cnt) {
    if(at_food == food and room_cnt == rooms) {
        return 1;
    }

    if(dp[at_food][room_cnt] != -1) {
        return dp[at_food][room_cnt];
    }

    ll res = 0;
    for(int i = 1; i <= max_cap; i++) {
        if(at_food + i <= food) {
            res += rec(at_food + i, room_cnt + 1);
        }
    }

    dp[at_food][room_cnt] = res;
    return res;
}
int main() {
    ios_base::sync_with_stdio(false);
    cin >> food >> rooms >> max_cap;
    memset(dp, -1, sizeof dp);
    cout << rec(0, 0) << endl;
    return 0;
}