#include <cstdio>
#include <iostream>
#include <sstream>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
using namespace std;
#define ll long long
#define _cle(m, a) memset(m, (a), sizeof(m))
#define repu(i, a, b) for(int i = a; i < b; i++)
#define MAXN 100050
#define eps 1e-5
bool vis[MAXN];
int flight[MAXN];
int m, n;
double d[MAXN];
int main()
{
    while(~scanf("%d%d", &n, &m) && (n + m))
    {
        _cle(flight, -1);
        _cle(d, 0.0);
        int x, y;
        for(int i = 0; i < m; i++) {
            scanf("%d%d", &x, &y);
            flight[x] = y;
        }
        int dt;
        for(int i = n - 1; i >= 0; i--)
            for(int j = 1; j <= 6; j++) {
              dt = i + j;
              while(flight[dt] > 0) dt = flight[dt];
              d[i] += (d[dt] + 1.0) / 6.0;
            }
        printf("%.4lf\n", d[0]);
    }
    return 0;
}