Help me in solving SEGTHREE problem

help
,
1

My issue

what’s wrong with this as i’m using brute force approach sliding window and its not giving correct

My code

#include <bits/stdc++.h>
using namespace std;

int main() {
    long long int t; cin>>t;
	while(t--){
	    long long int n;cin>>n;
	    vector<long long int>v(n);
	    for(long long int &i:v) cin>>i;
	    long long  int s = 0,b=0;
	    for(int i=0;i<n-2;i++){
	        long long int c = 0;
	        for(int j=0;j<3;j++){
	            s+=v[i+j];
	        }if(s%3!=0) {
	            v[i+2]+=3-s%3;
	            c+=3-s%3;
	        }b+=c;
	        s=0;
	    }
	    cout<<b<<endl;
	   // for(auto i:v){
	   //     cout<<i<<" ";
	   // }cout<<endl;
	}
}

Problem Link: Segment Three Practice Coding Problem - CodeChef