Something

#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
using namespace std;
int main()
{
   int n;
   cin>>n;
   vector <int> a(n+1,0);
   a[1]=1;
   a[0]=1;
   a[2]=1;
   for(int i=3;i<=n;i++)
   {
        a[i]=a[i-3]+a[i-2];        
   }
   cout<<a[n];
   getchar();
   getchar();
   return 0;
}