Fibbonachi

#include <iostream>
using namespace std;

int main() {
    int a=0,a1=0,a2=0,n;
    cin>>n;
    for(int i=0;i<=n;i++){
        if(i<=1) a=i;
        else a=a1+a2;
        a2=a1;
        a1=a;
    }
    cout<<a;
    return 0;
}