蒟蒻求助--c++5个wa了

#include<bits/stdc++.h>
using namespace std;
int n,f[5002];
int main(){
    //freopen("b.in","r",stdin);
    //freopen("b.out","w",stdout);
    cin>>n;
    f[1]=1;
    f[2]=2;
    for(int i=3;i<=n;i++){
        f[i]=f[i-1]+f[i-2];
    }
    cout<<f[n];
    //fclose(stdin);fclose(stdout);
    return 0;
}