Help me in solving EXACTSAVINGS problem

help
,
1

My issue

hi this is my code for the problem EXACTSAVINGS
what is wrong with my logic and code
please explain
if possible please let me know why i cant use this method

My code

#include <bits/stdc++.h>
#define ll long long
#define pll pair<long long ,long long > 
using namespace std;

int main() {
    // your code goes here
    int t;
    cin>>t;
    while(t--){
        int n,x,z;
        cin>>n>>x>>z;
        //cout<<n<<x<<z<<endl;
        ll curr_sum = 0;
        bool flag = false;
        ll a=0;
        for(int i=1;i<=n;i++){
            cin>>a;
            if(flag) continue;
            if((curr_sum+z)%x==0){
                //cout<<"YES"<<curr_sum<<z<<x<<endl;
                cout<<(curr_sum+z)/x<<endl;
                flag = true;
            }
            curr_sum += a;
            
        }
        if(!flag) cout<<"-1"<<endl;
    }
    return 0;
}

Problem Link: Exact Savings Practice Coding Problem - CodeChef