#include <bits/stdc++.h>
using namespace std;
#define rep(i, d, u) for(int i = d; i <= u; ++i)
#define dep(i, u, d) for(int i = u; i >= d; --i)
#define cep(n) while(n--)
#define gep(i, a) for(int i = firs[a]; i; i = neig[i])
int ured() {
	int re = 0;
	char ch;
	do {
		ch = getchar();
	} while('9' < ch || ch < '0');
	do {
		re = re * 10 + (ch ^ '0');
	} while('0' <= (ch = getchar()) && ch <= '9');
	return re;
}
void uwit(int da) {
	int ch[21], cn = 0;
	do {
		ch[++cn] = da - da / 10 * 10;
	} while(da /= 10);
	do {
		putchar('0' ^ ch[cn]);
	} while(--cn);
}
const int _maxn = 1011;
int n, m, u[_maxn], v[_maxn], w[_maxn], firs[_maxn], neig[_maxn << 1], arri[_maxn << 1], fath[_maxn], dfat[_maxn], fatp[_maxn];
int queu[_maxn], head, tail, frda[_maxn], frpo[_maxn], dans, dept[_maxn], atpo[_maxn];
bool visi[_maxn];
vector<int> edge[_maxn];
int find(int at) {
	return fath[at] == at ? at : fath[at] = find(fath[at]);
}
void dfs1(int at, int fa, int rt) {
	dfat[at] = fa, dept[at] = dept[fa] + 1, atpo[at] = rt;
	gep(i, at) {
		if(arri[i] != fa) {
			fatp[arri[i]] = i >> 1, dfs1(arri[i], at, rt);
		}
	}
}
void updb(int da, int at, int fr) {
	for(int i : edge[da]) {
		if(!visi[i]) {
			queu[++tail] = i, frda[i] = at, frpo[i] = fr;
		}
	}
}
void upda(int le, int ri, int fr) {
	while(le != ri) {
		if(dept[find(le)] > dept[find(ri)]) {
			updb(w[fatp[find(le)]], fatp[find(le)], fr), fath[find(le)] = find(dfat[find(le)]);
		} else {
			updb(w[fatp[find(ri)]], fatp[find(ri)], fr), fath[find(ri)] = find(dfat[find(ri)]);
		}
	}
}
int main() {
	n = ured(), m = ured();
	rep(i, 1, m) {
		u[i] = ured(), v[i] = ured(), w[i] = ured(), edge[w[i]] . push_back(i);
	}
	rep(i, 0, n - 1) {
		rep(j, 1, n) {
			firs[j] = dfat[j] = 0, fath[j] = j;
		}
		rep(j, 1, m) {
			if(visi[j]) {
				neig[j << 1] = firs[u[j]], firs[u[j]] = j << 1, arri[j << 1] = v[j];
				neig[j << 1 | 1] = firs[v[j]], firs[v[j]] = j << 1 | 1, arri[j << 1 | 1] = u[j];
			}
		}
		rep(j, 1, n) {
			if(!dfat[j]) {
				dfs1(j, 0, j);
			}
		}
		head = tail = dans = 0;
		for(int j : edge[i]) {
			queu[++tail] = j, frpo[j] = frda[j] = 0;
		}
		while(head < tail) {
			++head;
			if(atpo[u[queu[head]]] == atpo[v[queu[head]]]) {
				upda(u[queu[head]], v[queu[head]], queu[head]);
			} else {
				dans = queu[head];
				break;
			}
		}
		if(dans) {
			for(; ; dans = frpo[dans]) {
				visi[dans] = 1;
				if(frda[dans]) {
					visi[frda[dans]] = 0;
				} else {
					break;
				}
			}
		} else {
			uwit(i), putchar('\n');
			return 0;
		}
	}
	uwit(n), putchar('\n');
	return 0;
}