Hello, I have been trying a lot to solve Trail Maintence(LOJ), but I am getting RTE every time. I have been trying in many different ways, but at last I am getting RTE, don't know why. Can anyone help me debugging it please?

**Thanks in advance**

**My code**

```
/**
*First of all, I will be taking input until the whole graph is connected, and also,
*For every query, I have to output -1.
*After getting the whole graph connected, I have to perform my first MST.
*then I will output the mst as well.
*then I have to input every remained query and for every steps, the last added edge
*will make e cycle, and we have to remove the largest edge form the graph, which is unnecessary.. then.. output the ans it :D
**/
#include <bits/stdc++.h>
using namespace std;
const int N = 503;
struct pii{
int a;
int b;
int c;
pii(){a = 0,b = 0,c = 0;}
pii(int m,int n,int o){
a = m;
b = n;
c = o;
}
};bool operator<(pii a,pii b){return a.c < b.c;}
int n,pos,size,ans,parent[N],q,u,v,w;
vector<pii>mst;
pii ara[N+12];
void makeset(){for(int i = 0; i < N;i++)parent[i] = i;}
int find(int n){return n==parent[n]?n:parent[n]=find(parent[n]);}
void Union(int a,int b){ parent[find(a)] = find(b);}
int first_mst()
{
sort(mst.begin(),mst.end());
makeset();
size = mst.size();
int sum = 0;
for(int i = 0; i < size;i++){
if(find(mst[i].a) != find(mst[i].b)){
Union(mst[i].a,mst[i].b);
ara[pos++] = pii(mst[i].a,mst[i].b,mst[i].c);
sum += mst[i].c;
}
}
return sum;
}
void mst2()
{
size = pos;
sort(ara,ara+size);
makeset();
int indx = -1;
int sum = 0;
for(int i = 0; i < size;i++){
if(find(ara[i].a) != find(ara[i].b)){
Union(ara[i].a,ara[i].b);
sum += ara[i].c;
}
else{
indx = i;
}
}
if(indx == pos-1){
pos--;
}
else if(indx != -1){
pii mm = ara[pos-1];
ara[indx] = mm;
pos--;
}
printf("%d\n",sum);
}
int main()
{
//freopen("in.txt","r",stdin);
int t,caseno = 0;
scanf("%d",&t);
while(t--){
mst.clear();
pos = 0;
makeset();
scanf("%d%d",&n,&q);
printf("Case %d:\n",++caseno);
int k = n;
while(q--){
scanf("%d%d%d",&u,&v,&w);
mst.push_back(pii(u,v,w));
if(find(u) != find(v)){
k--;
Union(u,v);
}
if(k == 1)break;
printf("-1\n");
}
int ans = first_mst();
printf("%d\n",ans);
while(q--){
scanf("%d%d%d",&u,&v,&w);
ara[pos++] = pii(u,v,w);
mst2();
}
}
return 0;
}
```