cf B. The Fibonacci Segment

http://codeforces.com/contest/365/problem/B

 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #define maxn 200010
 #define LL __int64
 using namespace std;

 int n;
 LL a[maxn];

 int main()
 {
     while(scanf("%d",&n)!=EOF)
     {
         for(int i=; i<=n; i++)
         {
             scanf("%I64d",&a[i]);
         }
         int max1=min(,n);
         int len=;
         for(int i=; i<=n; i++)
         {
             if(a[i]==a[i-]+a[i-])
             {
                 len++;
                 max1=max(max1,len);
             }
             else len=;
         }
         printf("%d\n",max1);
     }
     return ;
 }