#include <stdio.h>
#define MAX 100
#define INF 1000000000

int main()
{
	FILE *inp=fopen("input.txt", "r");
	FILE *out=fopen("output.txt", "w");
	int A[MAX][MAX];
	int path[MAX];
	int used[MAX]={0};
	int i, j, n, snd, rcv, t1, t2, t3, min, curr;
	fscanf(inp, "%d\n%d %d", &n, &snd, &rcv);
	for(i=1;i<=n;i++)
	{
		path[i]=INF;
		for(j=1;j<=n;j++) A[i][j]=INF;
	}
	path[snd]=0;
	while(fscanf(inp, "%d %d %d", &t1, &t2, &t3)!=EOF)
	{
		A[t1][t2]=t3;
		A[t2][t1]=t3;
	}
	while(1)
	{
		min=INF;
		for(i=1;i<=n;i++)
		{
			 if(!used[i] && (path[i]<min))
			 {
				 min=path[i];
				 curr=i;
			 }
		}
		if(min==INF) break;
		used[curr]=1;
		for (i=1;i<=n;i++)
		{
			if(used[i]) continue;
			if(path[i]>(path[curr]+A[curr][i])) path[i]=(path[curr]+A[curr][i]);
		}
	}
	if(path[rcv]==INF) fprintf(out, "no\n"); else fprintf(out, "%d\n", path[rcv]);
	fclose(inp);
	fclose(out);
	return 0;
}