B. Jzzhu and Sequences
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
jzzhu has invented a kind of sequences, they meet the following property:
You are given x and y, please calculate fn modulo 1000000007 (109?+?7).
Input
The first line contains two integers x and y (|x|,?|y|?≤?109). The second line contains a single integer n (1?≤?n?≤?2·109).
Output
Output a single integer representing fn modulo 1000000007 (109?+?7).
Sample test(s)
input
2 33
output
input
0 -12
output
1000000006
Note
In the first sample, f2?=?f1?+?f3, 3?=?2?+?f3, f3?=?1.
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In the second sample, f2?=??-?1; ?-?1 modulo (109?+?7) equals (109?+?6).
题意：给你一个递推式，f2=f1+f3-->变形为：f[i]=f[i-1]-f[i-2];输入f[1]和f[2]；求第n个数的值；如果你想打表的话劝你放弃吧！肯定会超时的，还记得高中的等差序列吗！对这绝对是一个周期序列！而且周期为6；
#include<stdio.h>int main(){ __int64 a[10],x,y,n; int i; scanf("%I64d%I64d",&x,&y); a[1]=x;a[2]=y; for(i=3;i<=6;i++) a[i]=a[i-1]-a[i-2]; a[0]=a[6]; scanf("%I64d",&n); n=n%6; while(1) { if(a[n]<0) a[n]+=1000000007; else break; } printf("%I64d\n",a[n]%1000000007); return 0;}
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