CF 189A Cut Ribbon

#include<bits/stdc++.h>
using namespace std;
const int maxn = 4000 + 131;
int n, a, b, c;
int Dp[maxn];

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> a >> b >> c;
    memset(Dp,0,sizeof(Dp));
    Dp[a] = Dp[b] = Dp[c] = 1;
    for(int i = 0; i <= n; ++i)
    {
        /// 前一种状态必须是被填过的
        if(i >= a && Dp[i-a]) Dp[i] = max(Dp[i], Dp[i-a]+1);
        if(i >= b && Dp[i-b]) Dp[i] = max(Dp[i], Dp[i-b]+1);
        if(i >= c && Dp[i-c]) Dp[i] = max(Dp[i], Dp[i-c]+1);
    }
    cout << Dp[n] << endl;
}