#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll inf = 1e18;
const int M = 1e5+7;
int n,m,cnt,head[M],flag[M];
struct edge
{
    int v,nex;ll w;
}e[M*5];
void init(){
    cnt=0;memset(head,-1,sizeof(head));memset(flag,0,sizeof(flag));
}
void add(int u,int v,ll w){
    e[++cnt].v=v;e[cnt].w=w;e[cnt].nex=head[u];
    head[u]=cnt;
}
struct node
{
    int index,level;ll dis;
}d[M][2];
void dijkstra(int s,int t){
    for(int i=1;i<=n;i++)
        for(int j=0;j<=1;j++) d[i][j].dis=inf,d[i][j].index=i,d[i][j].level=j;
    priority_queue<node> q;d[s][0].dis=0;q.push(d[s][0]);
    while(!q.empty()){
        int u=q.top().index,lv=q.top().level;
        if(flag[u]) continue;
        flag[u]=1;

        for(int i=head[u];~i;i=e[i].nex){
            int v=e[i].v;ll w=e[i].w;
            if(d[v][lv].dis>d[u][lv].dis+w){
                d[v][lv].dis=d[u][lv].dis+w;
                q.push(d[v][lv]);
            }
            if(lv==0&&d[v][lv+1].dis>d[u][lv].dis+w/2){
                d[v][lv+1].dis=d[u][lv].dis+w/2;
                q.push(d[v][lv+1]);
            }
        }

    }
    ll ans=min(d[t][0].dis,d[t][1].dis);
    printf("%lld\n",ans);
}
int main(){

    return 0;
}