C++ :

#include<iostream>
#include<algorithm>
using namespace std;
const int N(4001);
int fib[N][N/3]={0};
//ifstream cin("exam1.in");
//ofstream cout("exam1.out");
void add(int *a,int *b,int *c)
{
    c[0]=max(a[0],b[0]);    
    for (int i=1;i<=c[0];i++)
    {
        c[i]+=a[i]+b[i];
        c[i+1]+=c[i]/10;
        c[i]%=10;
    }
    if (c[c[0]+1]) c[0]++;
}
void init()
{
    fib[1][0]=fib[2][0]=1;
    fib[1][1]=fib[2][1]=1;
    for (int i=3;i<N;i++)
        add(fib[i-1],fib[i-2],fib[i]);
}
void output(int n)
{
    for (int i=fib[n][0];i>0;i--) cout<<fib[n][i];
    cout<<endl;
}    
int main()
{
    init();
    int n;
    while (cin>>n)
        output(n);
    return 0;
}