View Code of Problem 23

#include <iostream>
#include <vector>
#include <string>
#include<algorithm>
using namespace std;
int main() {
    int n;
    cin >> n;
    while(n){
        if(n==1){
            cout << 1 << endl;
        }else if(n == 2){
            cout << 2 << endl;
        }else{
            long long int a=1,b=2,sum=0;
            for(int i=2; i<n; i++){
                sum = a+b;
                a = b;
                b = sum;
            }
            cout << sum << endl;
        }
        cin >> n;
    }
    return 0;
}