#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cassert>
using namespace std;const int MAX_NODE = 50010, MAX_EDGE = 200010, INF = 0x3f3f3f3f;
int TotNode, TotEdge, Ans;struct Edge
{int From, To, Weight;bool InTree;bool operator < (const Edge& a) const{return Weight < a.Weight;}
}_edges[MAX_EDGE];
int MaxEdgeP, MinEdgeP;struct LCT
{
private:static const int MAX_TREE_NODE = MAX_NODE + MAX_EDGE;struct Node{int Val;bool Rev;Node *Father, *LeftSon, *RightSon, *MinValP;bool IsRoot(){return !Father || (Father->LeftSon != this && Father->RightSon != this);}bool IsLeftSon(){return Father->LeftSon == this;}void Refresh(){MinValP = this;if (LeftSon && LeftSon->MinValP->Val < MinValP->Val)MinValP = LeftSon->MinValP;if (RightSon && RightSon->MinValP->Val < MinValP->Val)MinValP = RightSon->MinValP;}void Reverse(){swap(LeftSon, RightSon);Rev = !Rev;}void PushDown(){if (Rev){if (LeftSon)LeftSon->Reverse();if (RightSon)RightSon->Reverse();Rev = false;}}}_nodes[MAX_TREE_NODE];struct SplayTree{private:Node *InnerRoot;void PushDown(Node *cur){if (!cur->IsRoot()){PushDown(cur->Father);}cur->PushDown();}void Rotate(Node *cur){Node *gfa = cur->Father->Father;Node **gfaSon = cur->Father->IsRoot() ? &InnerRoot : cur->Father->IsLeftSon() ? &gfa->LeftSon : &gfa->RightSon;Node **faSon = cur->IsLeftSon() ? &cur->Father->LeftSon : &cur->Father->RightSon;Node **curSon = cur->IsLeftSon() ? &cur->RightSon : &cur->LeftSon;*faSon = *curSon;if (*faSon)(*faSon)->Father = cur->Father;*curSon = cur->Father;(*curSon)->Father = cur;*gfaSon = cur;(*gfaSon)->Father = gfa;(*curSon)->Refresh();cur->Refresh();}public:void Splay(Node *cur){PushDown(cur);while (!cur->IsRoot()){if (!cur->Father->IsRoot())Rotate(cur->Father->IsLeftSon() == cur->IsLeftSon() ? cur->Father : cur);Rotate(cur);}}}t;void Access(Node *cur){Node *prev = NULL;while (cur){t.Splay(cur);cur->RightSon = prev;cur->Refresh();prev = cur;cur = cur->Father;}}void MakeRoot(Node *cur){Access(cur);t.Splay(cur);cur->Reverse();}void MakePath(Node *u, Node *v){MakeRoot(v);Access(u);t.Splay(u);}void Link(Node *u, Node *v){MakeRoot(v);v->Father = u;}void Cut(Node *u, Node *v){MakePath(u, v);assert(v->Father == u);assert(u->LeftSon == v);u->LeftSon = NULL;v->Father = NULL;u->Refresh();}Node *FindRoot(Node *cur){while (cur->Father)cur = cur->Father;while (cur->LeftSon)cur = cur->LeftSon;return cur;}Node *GetMinNode(Node *u, Node *v){if (FindRoot(u) != FindRoot(v))return NULL;MakePath(u, v);return u->MinValP;}public:void SetNode(int v, int val){_nodes[v].Val = val;}void Link(int u, int v){Link(_nodes + u, _nodes + v);}void Cut(int u, int v){Cut(_nodes + u, _nodes + v);}int GetMinId(int u, int v){Node *ans = GetMinNode(_nodes + u, _nodes + v);if (ans == NULL)return -1;elsereturn ans - _nodes;}
}g;void InitBuild()
{sort(_edges + 1, _edges + TotEdge + 1);for (int i = 1; i <= TotEdge; i++)g.SetNode(TotNode + i, _edges[i].Weight);for (int i = 1; i <= TotNode; i++)g.SetNode(i, INF);int cnt = 0, curEdge = 0;while (cnt < TotNode - 1){curEdge++;int k = g.GetMinId(_edges[curEdge].From, _edges[curEdge].To);if (k == -1){cnt++;g.Link(_edges[curEdge].To, curEdge + TotNode);g.Link(curEdge + TotNode, _edges[curEdge].From);_edges[curEdge].InTree = true;MaxEdgeP = curEdge;}}Ans = _edges[MaxEdgeP].Weight - _edges[1].Weight;MinEdgeP = 1;
}int GetAns()
{for (int i = 1; i <= TotEdge; i++){if (_edges[i].InTree)continue;_edges[i].InTree = true;if (_edges[i].Weight > _edges[MaxEdgeP].Weight)MaxEdgeP = i;int cutEdge = g.GetMinId(_edges[i].From, _edges[i].To);assert(cutEdge != -1);g.Cut(_edges[cutEdge - TotNode].To, cutEdge);g.Cut(cutEdge, _edges[cutEdge - TotNode].From);_edges[cutEdge - TotNode].InTree = false;if (MaxEdgeP == cutEdge - TotNode)while (!_edges[MaxEdgeP].InTree)MaxEdgeP--;if (MinEdgeP == cutEdge - TotNode)while (!_edges[MinEdgeP].InTree)MinEdgeP++;Ans = min(Ans, _edges[MaxEdgeP].Weight - _edges[MinEdgeP].Weight);g.Link(_edges[i].To, i + TotNode);g.Link(i + TotNode, _edges[i].From);}return Ans;
}int main()
{scanf("%d%d", &TotNode, &TotEdge);for (int i = 1; i <= TotEdge; i++){scanf("%d%d%d", &_edges[i].From, &_edges[i].To, &_edges[i].Weight);while (_edges[i].From == _edges[i].To){TotEdge--;scanf("%d%d%d", &_edges[i].From, &_edges[i].To, &_edges[i].Weight);}}InitBuild();printf("%d\n", GetAns());return 0;
}