测评会员优惠活动进行中 · 开通 VIP,有效期内测评不限次 VIP 优惠中 · 测评不限次 立即查看

A1071. [COCI-2006_2007-contest3]#1 BICIKLI

编程题 普及/提高-

题目描述

A bicycle race is being organized in a land far, far away. There are N town in the land, numbered 1 through N. There are also M one-way roads between the towns. The race will start in town 1 and end in town
2.
How many different ways can the route be set? Two routes are considered different if they do not use the exact same roads.

输入格式

The first line of input contains two integers N and M (1 ≤ N ≤ 10 000, 1 ≤ M ≤ 100 000), the number of towns and roads.
Each of the next M lines contains two different integers A and B, representing a road between towns A and B.
Towns may be connected by more than one road.

输出格式

Output the number of distinct routes that can be set on a single line. If that number has more than nine digits, output only the last nine digits of the number. If there are infinitely many routes, output "inf".

输入输出样例

输入 #1
6 7 
1 3 
1 4 
3 2 
4 2 
5 6 
6 5 
3 4 
输出 #1
3
输入 #2
6 8 
1 3 
1 4 
3 2 
4 2 
5 6 
6 5 
3 4 
4 3 
输出 #2
inf
输入 #3
31 60 
1 3 
1 3 
3 4 
3 4 
4 5 
4 5 
5 6 
5 6 
6 7 
6 7 
… 
… 
… 
28 29 
28 29 
29 30 
29 30 
30 31 
30 31 
31 2 
31 2 
输出 #3
073741824
上一题 去做题 下一题