public static void solveOne() throws Exception {
int n = nextInt();
int m = nextInt();
int k = nextInt();
int w = nextInt();
char[][][] levels = new char[k][n][];
;
for (int i = 0; i < k; i++) {
for (int j = 0; j < n; j++) {
levels[i][j] = nextString().toCharArray();
}
}
int[][] cost = new int[k][k];
PriorityQueue<int[]> q =
new PriorityQueue<>(
k * k,
new Comparator<int[]>() {
@Override
public int compare(int[] o1, int[] o2) {
return o1[2] - o2[2];
}
});
for (int i = 0; i < k; i++) {
for (int j = i + 1; j < k; j++) {
int[] cur = {i, j, diff(levels[i], levels[j]) * w};
cost[i][j] = cur[2];
q.add(cur);
// px("edge", cur);
}
}
// px(q.size());
// for (int[] e: cost) px(e);
DisjointUnionSet djs = new DisjointUnionSet(k);
boolean[][] al = new boolean[k][k];
int finalCost = n * m * k;
for (; q.size() > 0; ) {
int[] edge = q.poll();
int p1 = djs.getPartitionId(edge[0]);
int p2 = djs.getPartitionId(edge[1]);
// px(edge, p1 == p2, edge[2]);
if (edge[2] > n * m) break;
if (p1 != p2) {
djs.unionElement(edge[0], edge[1]);
finalCost -= n * m - edge[2];
al[edge[1]][edge[0]] = true;
al[edge[0]][edge[1]] = true;
}
}
// for (boolean[] e: al) px(e);
pn(finalCost);
boolean[] ex = new boolean[k];
for (int i = 0; i < k; i++) {
if (!ex[i]) {
dfs(i, -1, ex, k, al);
}
}
}
public static void dfs(int at, int from, boolean[] ex, int k, boolean[][] al) {
ex[at] = true;
pn((at + 1) + " " + (from + 1));
for (int i = 0; i < k; i++) {
if (!ex[i] && al[i][at]) {
// px(i, at);
dfs(i, at, ex, k, al);
}
}
}
