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#include<cstring>
#include<cmath>
#include<cctype>
#include<algorithm>
#include<vector>
#include<queue>
#include<stack>
#include<climits>
#include<iostream>
#include<map>
#define FOR(i,a,b,c) for(int i=(a);i<=(b);i+=(c))
#define ROF(i,a,b,c) for(int i=(a);i>=(b);i-=(c))
#define FORL(i,a,b,c) for(long long i=(a);i<=(b);i+=(c))
#define ROFL(i,a,b,c) for(long long i=(a);i>=(b);i-=(c))
#define FORR(i,a,b,c) for(register int i=(a);i<=(b);i+=(c))
#define ROFR(i,a,b,c) for(register int i=(a);i>=(b);i-=(c))
#define lowbit(x) x&(-x)
#define LeftChild(x) x<<1
#define RightChild(x) (x<<1)+1
#define RevEdge(x) x^1
#define FILE_IN(x) freopen(x,"r",stdin);
#define FILE_OUT(x) freopen(x,"w",stdout);
#define CLOSE_IN() fclose(stdin);
#define CLOSE_OUT() fclose(stdout);
#define IOS(x) std::ios::sync_with_stdio(x)
#define Dividing() printf("-----------------------------------n");
namespace FastIO{
const int BUFSIZE = 1 << 20;
char ibuf[BUFSIZE],*is = ibuf,*its = ibuf;
char obuf[BUFSIZE],*os = obuf,*ot = obuf + BUFSIZE;
inline char (){
if(is == its)
its = (is = ibuf)+fread(ibuf,1,BUFSIZE,stdin);
return (is == its)?EOF:*is++;
}
inline int getint(){
int res = 0,neg = 0,ch = getch();
while(!(isdigit(ch) || ch == '-') && ch != EOF)
ch = getch();
if(ch == '-'){
neg = 1;ch = getch();
}
while(isdigit(ch)){
res = (res << 3) + (res << 1)+ (ch - '0');
ch = getch();
}
return neg?-res:res;
}
inline void flush(){
fwrite(obuf,1,os-obuf,stdout);
os = obuf;
}
inline void putch(char ch){
*os++ = ch;
if(os == ot) flush();
}
inline void putint(int res){
static char q[10];
if(res==0) putch('0');
else if(res < 0){putch('-');res = -res;}
int top = 0;
while(res){
q[top++] = res % 10 + '0';
res /= 10;
}
while(top--) putch(q[top]);
}
inline void space(bool x){
if(!x) putch('n');
else putch(' ');
}
}
inline void read(int &x){
int rt = FastIO::getint();
x = rt;
}
inline void print(int x,bool enter){
FastIO::putint(x);
FastIO::flush();
FastIO::space(enter);
}
const int MAXN = 3e3 + 50;
const int MAXM = 2e4 + 10;
int n,m,a[MAXN];
struct Edge{
int next,to;
double dis;
}Graph[MAXM];
int head[MAXN],cnt;
int visited[MAXN],flag;
double dist[MAXN], l = -1e6, r = 1e6;
inline void Add_Edge(int from,int to,double dis){
Graph[++cnt] = (Edge){head[from],to,dis};
head[from] = cnt;
}
inline void check(int limit,double d){
visited[limit] = true;
for(int i=head[limit];i;i=Graph[i].next){
if(dist[Graph[i].to] > dist[limit] + Graph[i].dis - d){
if(visited[Graph[i].to] || flag) {flag = 1; break;}
dist[Graph[i].to] = dist[limit] + Graph[i].dis - d;
check(Graph[i].to,d);
}
}
visited[limit] = 0;
}
int main(int argc,char *argv[]){
scanf("%d%d",&n,&m);
FOR(i,1,m,1){
int u,v; scanf("%d%d",&u,&v);
double d; scanf("%lf",&d);
Add_Edge(u,v,d);
}
while(r - l > 1e-10){
double mid = (l + r)/2;
memset(dist,0,sizeof(dist));
memset(visited,false,sizeof(visited)); flag = 0;
FOR(i,1,n,1){
check(i,mid); if(flag) break;
}
if(flag) r = mid;
else l = mid;
}
printf("%.8lf",l);
return 0;
}
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