PROG-T1112: Inversion

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

const int N = 1e4;
const int MD = 2012;

int dp[N + 1], qs[N + 1];

int main(){

    int x, k;
    scanf("%d%d", &x, &k);
    dp[0] = 1;
    dp[1] = 1;
    for(int i = 0; i <= 6; ++i){
        qs[i] = (i < 1 ? 0 : qs[i - 1]) + dp[i];
    }
    for(int i = 3; i <= x; ++i){
        int upb = min(k, i * (i - 1) / 2);
        for(int j = 0; j <= upb; ++j){
            dp[j] = (MD + qs[j] - (j - i < 0 ? 0 : qs[j - i])) % MD;
        }
        upb = min(k, i * (i + 1) / 2);
        for(int j = 0; j <= upb; ++j){
            qs[j] = ((j < 1 ? 0 : qs[j - 1]) + dp[j]) % MD;
        }
    }
    cout << dp[k];

    return 0;
}