#include <iostream>
#include <cstdio>
#include <cstring>
#include <map>
using namespace std;
const int maxn = 100000+10;
double dp[maxn];
map<int,int> t;
map<int,int> flight;
int n,m;
void dfs(int sta,int x){
    if(t[x]==0){
        flight[sta] = x;
    }else{
        dfs(sta,t[x]);
    }
}
void init(){
    for(map<int,int>::iterator it = t.begin(); it != t.end(); it++){
        dfs(it->first,it->second);
    }
}
int main(){

    while(cin >> n >> m && n+m){
        t.clear();
        flight.clear();
        while(m--){
            int a,b;
            scanf("%d%d",&a,&b);
            t[a] = b;
        }
        init();
        dp[n] = 0;
        for(int i = n-1; i >= 0; i--){
            dp[i] = 1;
            for(int k = 1; k <= 6; k++){
                if(i+k <= n){
                    if(flight[i+k]==0){
                        dp[i] += dp[i+k]/6;
                    }else{
                        dp[i] += dp[flight[i+k]]/6;
                    }

                }
            }
        }
        printf("%.4lf\n",dp[0]);

    }
    return 0;
}