#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
double a[100005];
int vis[100005];
int main()
{
    int n,m;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        if(n==0&&m==0) break;
        memset(a,0,sizeof(a));
        memset(vis,-1,sizeof(vis));
        for(int i=0;i<m;i++)
        {
            int a,b;
            scanf("%d%d",&a,&b);
            vis[a]=b;
        }
        for(int i=n-1;i>=0;i--)
        {
            if(vis[i]==-1)
            {
                for(int j=1;j<=6;j++)
                a[i]+=a[i+j]/6.0;
                a[i]+=1;

            }
            else a[i]=a[vis[i]];

        }
        printf("%.4f\n",a[0]);
    }
    return 0;
}