#include <stdio.h>
#include <limits.h>

#define INF INT_MAX
int N;
int Dist[500];
int Q[500];
int Visited[500];
int Graph[500][500];

void Dijkstra(int b){
     int H = 0;
     int T = -1;
     int j,k;

Dist[b] = 0;

Q[T+1] = b;
T = T+1;

while(T>=H){
    j = Q[H];
    Visited[j] = 1;
    for (k = 0;k < N; k++){
        if(!Visited[k] && Dist[k] > Graph[j][k] + Dist[j] && Graph[j][k] != -1){
            Dist[k] = Dist[j]+Graph[j][k];
            Q[T+1] = k;
            T = T+1;
        }
    }

    H = H+1;
}
}  

int main(){

int src,target,m;
int a,w,b,i,j;

scanf("%d%d%d%d",&N,&m,&src,&target);

for(i = 0;i < N;i ++){
    for(j = 0;j < N;j++){
        Graph[i][j] = -1;
    }
}

for(i = 0; i< N; i++){
    Dist[i] = INF;
    Visited[i] = 0;
}


for(i = 0;i < m; i++){
    scanf("%d%d%d",&a,&b,&w);
    a--;
    b--;
    Graph[a][b] = w;
    Graph[b][a] = w;
}

Dijkstra(src-1);


if(Dist[target-1] == INF){
    printf("NO");
}else {
    printf("YES\n%d",Dist[target-1]);
}

return 0;
}