求大佬指点！为啥这样ac不了？

链接：https://ac.nowcoder.com/acm/contest/72369/D

#include<bits/stdc++.h>

using namespace std;

#define N 3005

long long a[N],f[N][N];//dp数组，dp[i][j]表示前i个数中除以k的余数为j的当前最大和

int n,k;

int main(){

cin >> n >> k;

for(int i = 1; i <= n; i ++) {cin >> a[i];}

memset(f,-0x3f,sizeof f);

long long maxv = -0x3f3f3f3f;

f[0][0] = 0;

for(int i = 1; i <= n; i ++){

for(int j = 0; j < k; j ++){

f[i][j] = max(f[i - 1][(j - a[i] + k) % k] + a[i],f[i - 1][j]);

//能ac的状态方程： f[i][(j + a[i]) % k] = max(f[i - 1][j] + a[i],f[i - 1][(j + a[i]) % k]);

}

}

for(int i = 1; i <= n; i ++) maxv = max(maxv,f[i][0]);

if(maxv > 0)cout << maxv << endl;

else cout << -1 << endl;

return 0;

}