12184: 函数求值

Memory Limit:32 MB Time Limit:1.000 S
Judge Style:Text Compare Creator:
Submit:1 Solved:0

Description

给定正整数N,函数F(N)表示小于等于N的自然数中1和2的个数之和,例如:1,2,3,4,5,6,7,8,9,10序列中1和2的个数之和为3,因此 F(10)=3。输入N,求F(N)的值,1=<N<=10^100(10的100次方)若F(N)很大,则求F(N)mod20123的值

Sample Input Copy

10
10

Sample Output Copy

3
3