http://acm.hust.edu.cn/vjudge/contest/view.action?cid=31329#problem/N
#include<map>
#include<set>
#include<list>
#include<cmath>
#include<ctime>
#include<deque>
#include<stack>
#include<bitset>
#include<cstdio>
#include<vector>
#include<cstdlib>
#include<cstring>
#include<iomanip>
#include<numeric>
#include<sstream>
#include<utility>
#include<iostream>
#include<algorithm>
#include<functional>
using namespace std ;
int n , k , m ;
const int maxn = 55 ;
long long f[ maxn ][ maxn ] ;
int main()
{
while( scanf( "%d%d%d" , &n , &k , &m ) != EOF )
{
memset( f , 0 , sizeof( f ) ) ;
for( int i = 0 ; i <= n && i <= m ; ++i )
{
f[ 1 ][ i ] = 1 ;
}
for( int i = 2 ; i <= k ; ++i )
{
for( int j = i ; j <= n ; ++j )
{
for( int k = 1 ; k <= m && j - k > 0 ; ++k )
{
f[ i ][ j ] += f[ i - 1][ j - k ] ;
}
}
}
printf( "%lld\n" , f[ k ][ n ] ) ;
}
return 0 ;
}