// Merges two points with 5 neibs
void Mesh::mergeVertex() {
calcEdge();
for(size_t i = 0; i < vb.size(); i++){
int v1 = vb[i];
int v2 = ve[i];
int n1 = pts[v1].neib.size();
int n2 = pts[v2].neib.size();
if( n1 == 5 && n2 == 5 ){
// Dont merge futher these points
pts[v1].neib.push_back(-1);
pts[v2].neib.push_back(-1);
changeVertex(v1, v2);
delVertex(v2);
for (const int itr : pts[v2].neibTria) {
Triangle &tr = tri[itr];
if( tr.v1 == v2 )
tr.v1 = v1;
if( tr.v2 == v2 )
tr.v2 = v1;
if( tr.v3 == v2 )
tr.v3 = v1;
}
delTria(tria1[i]);
delTria(tria2[i]);
}
}
pack();
calcNeigTria();
calcNeigbor();
}
int main() {
// freopen("in.txt", "r+t", stdin);
// freopen("out.txt", "w+t", stdout);
int n, m, q, t;
int cases = 0;
while (scanf("%d %d", &n, &m) == 2 && n) {
tree.init();
for (int i = 1; i <= n; i++)
scanf("%d", &w[i]);
for (int i = 1; i <= m; i++)
scanf("%d %d", &edgeX[i], &edgeY[i]);
int exists[MAXM] = {};
for (int i = 1; i <= m; i++)
exists[i] = 1;
for (q = 0; scanf("%s", cmd[q]) == 1 && cmd[q][0] != 'E'; q++) {
if (cmd[q][0] == 'D')
scanf("%d", &QX[q]), exists[QX[q]] = 0;
else if (cmd[q][0] == 'C')
scanf("%d %d", &QX[q], &QY[q]), t = QY[q], QY[q] = w[QX[q]], w[QX[q]] = t;
else if (cmd[q][0] == 'Q')
scanf("%d %d", &QX[q], &QY[q]);
}
for (int i = 1; i <= n; i++)
root[i] = null;
for (int i = 1; i <= n; i++)
tree.insert(root[i], w[i]);
initDisjointSet(n);
for (int i = 1; i <= m; i++)
if (exists[i] == 1)
joint(edgeX[i], edgeY[i]);
double ret = 0, cnt = 0;
for (int i = q - 1; i >= 0; i--) {
if (cmd[i][0] == 'D')
joint(edgeX[QX[i]], edgeY[QX[i]]);
else if (cmd[i][0] == 'C')
changeVertex(QX[i], QY[i]);
else if (cmd[i][0] == 'Q') {
cnt++;
node* v = tree.rkth_element(root[findp(QX[i])], QY[i]);
if (v == null) /*puts("undefined")*/;
else ret += v->key/*, printf("kth %d\n", v->key)*/;
}
}
ret /= cnt;
printf("Case %d: %lf\n", ++cases, ret);
}
return 0;
}
