URAL 1114 Boxes (dp)

#include<iostream>
#include<math.h>
#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<string>
#include<vector>
#include<queue>
#include<map>
#include<set>
using namespace std;
#define B(x) (1<<(x))
void cmax(int& a,int b){ if(b>a)a=b; }
void cmin(int& a,int b){ if(b<a)a=b; }
typedef unsigned long long ll;
const int oo=0x3f3f3f3f;
const ll OO=1LL<<61;
const int MOD=1000007;
const int maxn=55;
ll dp[22][17][17];

int main(){
    //freopen("E:\\read.txt","r",stdin);
    int n,A,B;
    while(scanf("%d %d %d",&n,&A,&B)!=EOF){
        memset(dp,0,sizeof dp);
        dp[0][0][0]=1;
        for(int i=1;i<=n;i++){
            for(int j=0;j<=A;j++){
                for(int k=0;k<=B;k++){
                    for(int jj=0;jj<=j;jj++){
                        for(int kk=0;kk<=k;kk++){
                            dp[i][j][k]+=dp[i-1][jj][kk];
                        }
                    }
                }
            }
        }
        ll ans=0;
        for(int i=0;i<=A;i++){
            for(int j=0;j<=B;j++)
                ans+=dp
[i][j];
        }
        cout<<ans<<endl;
    }
    return 0;
}