import std.stdio;
import std.string;
import std.array;
import std.typecons;
import std.typetuple;
import std.container;
import std.algorithm;
import std.conv;
import std.math;
import std.format;

alias TypeTuple tie;

void readlnToken(T...)(auto ref T args)
{
    import std.stdio;
    import std.conv;
    import std.string;
    import std.array;

    auto line = split(readln().strip);
    foreach(ref arg; args)
    {
        arg = to!(typeof(arg))(line[0]);
        line = line[1..$];
    }
    assert(line.empty()); // got all token??
}
const Mod = cast(long)(1E+9)+7;

void solve()
{
    int N,S,K;
    readlnToken(N,S,K);

    S -= N*(N-1)/2 * K;
    if (S < 0)
    {
        writeln(0);
        return;
    }
    auto dp = new long[][](N+1,S+1);
    dp[0][0] = 1;
    foreach(i;1..N+1)
    {
        foreach(j;0..S+1)
        {
            dp[i][j] = dp[i-1][j] % Mod;
            int k = j - (N-i+1);
            if (k >= 0)
                (dp[i][j] += dp[i][k] % Mod) %= Mod;
        }
    }
    writeln(dp[N][S]);
}

void main()
{
       solve();
}