How to resolve time limit exceeded error in following code Time limit is 1 sec

#include
#include
#include
using namespace std;

int main() {
int t;
scanf("%d",&t);

for(int i=0;i<t;i++)
{
    int n;
    scanf("%d",&n);
    int f[n];
    f[0]=0;
    f[1]=1;
    for(int i=2;i<n;i++)
    {
        f[i]=f[i-1]+f[i-2];
    }
    vector<int> d;
    for(int i=0;i<n;i++)
    {
        d.push_back(f[i]%10);
    }
    vector<int> e;
    
    while(d.size()>1)
    {
    for(int i=1;i<d.size();i=i+2)
    {
       e.push_back(d[i]);
    }
    d.clear();
    for(int i=0;i<e.size();i++)
    {
        d.push_back(e[i]);
    }
    e.clear();
    }
    for(int i=0;i<d.size();i++)
    {
        printf("%d",d[i]);
    }
    
}
return 0;

}

what is the question??