Score : 800 points
Snuke has a string x of length N.
Initially, every character in x is 0
.
Snuke can do the following two operations any number of times in any order:
0
.1
.Find the number of different strings that x can be after Snuke finishes doing operations. This count can be enormous, so compute it modulo (10^9+7).
Input is given from Standard Input in the following format:
N A B
Print the number of different strings that x can be after Snuke finishes doing operations, modulo (10^9+7).
4 2 3
11
For example, x can be 0011
or 1111
in the end, but cannot be 0110
.
10 7 2
533
1000 100 10
828178524