题解

#include <bits/stdc++.h>
using namespace std;
int main(){
long long qb[61];
int n;
cin>>n;
qb[1]=1;
qb[2]=2;
for(int i=3;i<=n;i++)
qb[i]=qb[i-1]+qb[i-2];
cout<<qb[n]<<endl;
return 0;
}