C++ :

#include <cstdio>
#include <algorithm>
using namespace std;

struct vi {
	int start;
	int end;
	int cost;
} edge[5000], et;

int p[101];

int Find(int n) {
	return n == p[n] ? n : p[n] = Find(p[n]);
}

bool cmp(vi a, vi b) {
	return a.cost < b.cost;
}

int main() {
	int n, m, i, k, sum, flag, ST, EN;
	while (scanf("%d%d", &n, &m) != EOF, n) {
		for (i = 1; i <= m; i++)
			p[i] = i;
		for (k = i = 0; i < n; i++) {
			scanf("%d%d%d", &et.start, &et.end, &et.cost);
			edge[k++] = et;
		}
		sort(edge, edge + k, cmp);
		for (sum = i = 0; i < k; i++) {
			ST = Find(edge[i].start);
			EN = Find(edge[i].end);
			if (ST != EN) {
				p[ST] = EN;
				sum += edge[i].cost;
			}
		}
		for (flag = 0, i = 1; i <= m; i++)
			if (p[i] == i)
				flag++;
		if (flag == 1)
			printf("%d\n", sum);
		else
			puts("Error!");
	}
	return 0;
}