80分玄关

#include <bits/stdc++.h>
using namespace std;
int n;
struct node
{
    int a[310];
    int len = 0;
    void out()
    {
        for(int t = len;t >= 0;t--)
        {
            printf("%d",a[t]);
        }
    }
};
node operator + (node a,node b)  
{
    node cnt = a;
    cnt.len = max(a.len,b.len);
    int maxn = cnt.len;
    for(int i = 0;i <= b.len;i++)
    {
        cnt.a[i] += b.a[i];
        maxn = max(maxn,i);
        if(cnt.a[i] >= 10)
        {
            cnt.a[i + 1]++;
            cnt.a[i] %= 10;
            maxn = max(maxn,i + 1);
        }
    }
    cnt.len = maxn;
    return cnt;
}
node ans[5010];
int main()
{
    scanf("%d",&n); 
    ans[0].a[0] = 1;
    ans[1].a[0] = 1;
    for(int t = 2;t <= n;t++)
    {
        ans[t] = ans[t - 1] + ans[t - 2];
    }
    ans[n].out();
    return 0;
 }