x+2y+3z=n非负整数解

#include <iostream>
#include <string.h>
#include <stdio.h>

using namespace std;
typedef long long LL;

LL work(LL n)
{
    LL ans = ;
    for(int k = ; k <= n / ; k++)
        ans += (n -  * k) /  + ;
    return ans;
}

int main()
{
    LL n;
    while(cin>>n)
        cout<<work(n)<<endl;
    return ;
}

#include <iostream>
#include <string.h>
#include <stdio.h>

using namespace std;
typedef long long LL;

LL work(LL n)
{
    LL k = n / ;
    LL t = (k + ) * n -  * k * (k + ) / ;
    LL ans = k + ;
    if(k & ) t -= (k + ) / ;
    else if(n & ) t -= (k /  + );
    else t -= k / ;
    t >>= ;
    return ans + t;
}

int main()
{
    LL n;
    while(cin>>n)
        cout << work(n) << endl;
    return ;
}