#include<bits/stdc++.h>
using namespace std;
const int N=1010, inf=0x3f3f3f3f;
int d[N][N], a[N][N], rk[N][N];

int main()
{
    int n, m; scanf("%d %d", &n, &m);

    memset(d, 63, sizeof(d)); memset(a, 63, sizeof(a));
    for(int i=1; i<=n; i++) d[i][i] = a[i][i] = 0;
    
    for(int i=1, x, y, z; i<=m; i++)
    {
        scanf("%d %d %d", &x, &y, &z);
        if (d[x][y] < z) continue;
        d[x][y] = d[y][x] = z;
        a[x][y] = a[y][x] = z;
    }
    
    for(int k = 1; k <= n; k++)//Floyed 跑最短路
        for(int i = 1; i <= n; i++) if(i != k)
            for(int j = 1; j <= n; j++) if(j != k && j != i)
                d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
    
    for(int i=1; i<=n; i++)
    {
        for(int j=1; j<=n; j++) rk[i][j] = j;
        for(int j=1; j < n; j++) for(int k=j+1; k <= n; k++) //直接冒泡给到每个点距离排序
            if(d[i][rk[i][j]] > d[i][rk[i][k]]) swap(rk[i][j], rk[i][k]);
    }
    
    int ans = inf;
    for(int i=1; i<=n; i++) ans = min(ans, d[i][rk[i][n]] * 2);
    for(int i=1; i<=n; i++) for(int j=1; j<=n; j++) if(i != j && a[i][j] != inf)//直接枚举边
    {
        for(int p = n, k = n-1; k >= 1; k--)//倒序
        {
            if(d[j][rk[i][k]] > d[j][rk[i][p]]) //每找到一个峰点都算一次
            {
                ans = min(ans, d[i][rk[i][k]] + d[j][rk[i][p]] + a[i][j]);
                p = k;
            }
        }
    }
    printf("%d\n", ans);
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int N=1010,inf=0x3f3f3f3f;
int d[N][N], a[N][N], rk[N][N];

int main()
{
	int n,m;scanf("%d %d", &n, &m);

	memset(d,63,sizeof(d));memset(a,63,sizeof(a));
	for(int i=1;i<=n;i++) d[i][i]=a[i][i] = 0;
	
	for(int i=1,x,y,z;i<= m;i++)
	{
		scanf("%d %d %d", &x, &y, &z);
		if (d[x][y] < z) continue;
		d[x][y] = d[y][x] = z;
		a[x][y] = a[y][x] = z;
	}
	
	for(int k = 1; k <= n; k++)//Floyed 跑最短路
		for(int i = 1; i <= n; i++)if(i!=k)
			for(int j = 1; j <= n; j++)if(j!=k && j!=i)
				d[i][j] =min(d[i][j], d[i][k] + d[k][j]);
	
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=n;j++)rk[i][j]=j;
		for(int j=1;j<n;j++) for(int k=j+1;k<=n;k++) //直接冒泡给到每个点距离排序
			if(d[i][rk[i][j]]>d[i][rk[i][k]])swap(rk[i][j],rk[i][k]);
	}
	
	int ans=inf;
	for(int i=1;i<=n;i++) ans = min(ans, d[i][rk[i][n]] * 2);
	for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)if(i!=j && a[i][j]!=inf)//直接枚举边
	{
		for(int p=n,k=n-1;k>=1;k--) //倒序
		{
			if(d[j][rk[i][k]]>d[j][rk[i][p]]) //每找到一个峰点都算一次
			{
				ans=min(ans, d[i][rk[i][k]] + d[j][rk[i][p]] + a[i][j]);
				p = k;
			}
		}
	}
	printf("%d\n", ans);
	return 0;
}