#define F(v)d[j]>d[++k]+v?d[j]=d[k]+v:0
d['@@'];n,p;main(a,b,c,j,k){scanf("%d%d",&n,&p);for(memset(j=d+p+1,99,12);j++<p||~scanf("%d%d%d",&a,&b,&c,j=0);F(b),F(c),F(1))d[k=j]+=a;n=!printf("%f",1.**d/n);}