#include <string>
#include <vector>
using namespace std;
typedef unsigned long long ll;
ll solution(int n) {
int dp[600001];
dp[0] = 0;
dp[1] = 1;
dp[2] = 2;
for(int i = 3; i <= n; i++){
dp[i]= (dp[i-1]+dp[i-2])%1000000007;
}
ll answer = dp[n];
return answer;
}