实在看不出来了，求大佬回复

#include <bits/stdc++.h>
using namespace std;

int n, k, carry;
int f[5010][1010];

int main() {
    cin >> n;
    f[1][1] = 1; 
    f[2][1] = 2; 
    
    for (int i = 3; i <= n; i++) {
        carry = 0;
        for (int j = 1; j <= 1000; j++) {
            f[i][j] = f[i-1][j] + f[i-2][j] + carry;
            carry = f[i][j] / 10; 
            f[i][j] %= 10;        
        }
	}
    k = 1000;
    while (k > 1 && f[n][k] == 0) k--;
    for (int i = k; i >= 1; i--) {
        cout << f[n][i];
    }
    
    return 0;
}