Hat's Fibonacci

Description

A Fibonacci sequence is calculated by adding the previous two members the sequence, with the first two members being both 1.
F(1) = 1, F(2) = 1, F(3) = 1,F(4) = 1, F(n>4) = F(n - 1) + F(n-2) + F(n-3) + F(n-4)
Your task is to take a number as input, and print that Fibonacci number.

 

Input

Each line will contain an integers. Process to end of file.

 

Output

For each case, output the result in a line.

 

Sample Input

100

 

Sample Output

4203968145672990846840663646

#include<stdio.h>
#include<algorithm>
using namespace std;

struct bign{
 int num[2100];
 int len;
 bign(){
  for(int i=0;i<2100;i++)
  {
   num[i]=0;
  }
  len=0;
 }
};
bign x[5];
bign add(bign x,bign y){
 bign c;
 int flag=0,sum;
 int i;
 for(i=0;i<x.len||i<y.len;i++){
  sum=0;
  sum=x.num[i]+y.num[i]+flag;
  c.num[i]=sum%10;
  flag=sum/10;
 }
 c.len=max(x.len,y.len);
 if(flag!=0){
 c.num[i]=flag;
 c.len++;
 }
 return c;
}
bign add2(bign a,bign b,bign c,bign d){
 bign x,y;
 x=add(a,b);
 y=add(c,d);
 return add(x,y);
}
int main()
{
 int n;
 
 while(scanf("%d",&n)!=EOF)
 {
  for(int k=0;k<=3;k++){
   for(int i=0;i<=x[k].len;i++)
   x[k].num[i]=0;
   x[k].num[0]=1;
   x[k].len=1;
       }
  for(int i=5;i<=n;i++){
  x[4]=add2(x[0],x[1],x[2],x[3]);
  for(int i=0;i<4;i++){
   for(int j=0;j<x[i+1].len;j++)
  x[i].num[j]=x[i+1].num[j];
  x[i].len=x[i+1].len;
  }

  }
  for(int i=x[3].len-1;i>=0;i--)
  printf("%d",x[3].num[i]);
  printf("\n");
  }
}