hdu4405--Aeroplane chess(求期望)

//Accepted    4405    234MS    8248K    757 B    Java
import java.util.Scanner;

public class Main {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

while(sc.hasNext()){

int n = sc.nextInt();
int m = sc.nextInt();
if(n == 0 && m == 0) break;
double e[] = new double[n+1];
int useif[] = new int[n+1];
for(int i = 0; i < m ; ++i){
int a = sc.nextInt();
int b = sc.nextInt();
useif[a] = b;
}
e
= 0;
for(int i = n - 1; i >= 0 ; --i){
if(useif[i] > 0){
e[i] = e[useif[i]];
continue;
}
e[i] = 1;
for(int j = 1; j < 7; j++){
if(i + j > n) break;
else
e[i] += e[i+j]/6;
}
}
System.out.printf("%.4f",e[0]);
System.out.println();
}
}

}