#include<bits/stdc++.h>
using namespace std;
#define fr first
#define sc second
#define pb push_back
typedef long long ll;
typedef pair<int,int>pii;
const int inf = 0x3f3f3f3f;
const int mod = 1000000007;
const double pi = acos(-1.0);
const ll INF = 0x3f3f3f3f3f3f3f3f;
#define rep(i,x,y) for(auto i=(x);i<=(y);++i)
#define dep(i,x,y) for(auto i=(x);i>=(y);--i)
const int dx[] = { -1,0,1,0 }, dy[] = { 0,1,0,-1 };
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll poww(ll a, ll b) { ll s = 1; while (b) { if (b & 1)s = (s * a) % mod; a = (a * a) % mod; b >>= 1; }return s % mod; }
/*----------------------------------------------------------------------------------------------------------------------*/

const int N = 1e6 + 11;
ll n,m;
int a[5555];
void solve()
{
    while(cin>>n>>m)
    {
        memset(a,0,sizeof(a));
        int l,r,w;
        while(m--)
        {
            cin>>l>>r>>w;
            if(l==r)continue;
            a[l]+=w;
            a[r]+=w;
        }
        sort(a+1,a+n+1);
        cout<<a[1]<<endl;
    }
}


/*----------------------------------------------------------------------------------------------------------------------*/
int main()
{
    ios::sync_with_stdio(false); cin.tie(0);
    ll T = 1;
    // cin >> T;
    while (T--)solve();
    return 0;
}