Bar Codes

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 ;
}