为啥会超时呢

#include<bits/stdc++.h>
using namespace std;
int i = 10000, j = 0;
int k;
int a[5] = {1, 0, 0, 0, 0};
int s1 ,s2 ,s3;
int main(){
    cin>> k;
    for(i; i <= 30000; i++) {
        a[5] = i % 10;
        a[4] = (i / 10) % 10;
        a[3] = (i / 100) % 10;
        a[2] = (i / 1000) % 10;
        a[1] = (i / 10000) % 10;
        s1 = a[1]*100 + a[2]*10 + a[3];
        s2 = a[2]*100 + a[3]*10 + a[4];
        s3 = a[3]*100 + a[4]*10 + a[5];
        if(s1 % k == 0 && s2 % k == 0 && s3 % k == 0) {
            cout<< i << endl;
            j++;
        }
    }
    if(j == 0) cout<< "No" << endl;
        return 0;
}