Nth Fibonacci Number

 Nth Fibonacci Number

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Nth term of Fibonacci series F(n), where F(n) is a function, is calculated using the following formula -

    F(n) = F(n-1) + F(n-2), 
    Where, F(1) =  1, 
           F(2) = 1

Provided N you have to find out the Nth Fibonacci Number.

Input Format :

The first line of each test case contains a real number ‘N’.

Output Format :

For each test case, return its equivalent Fibonacci number.

Constraints:

1 <= N <= 10000     
Where ‘N’ represents the number for which we have to find its equivalent Fibonacci number.

Time Limit: 1 second

Sample Input 1:

6

Sample Output 1:

8

Explanation

Now the number is ‘6’ so we have to find the “6th” Fibonacci number
So by using the property of the Fibonacci series i.e 

[ 1, 1, 2, 3, 5, 8, 13, 21]
So the “6th” element is “8” hence we get the output.

#include<iostream>
using namespace std;

int main(){
    //Write your code here. 
    int n1,n2;
    n1=n2=1;
    int n;
    cin>>n;
    int fab=0;
    if(n==1 || n==2)
        cout<<1<<endl;
    else
    {
        for(int i=2;n>i;i++){
            fab=n1+n2;
            n1=n2;
            n2=fab;
        }
    cout<<fab<<endl;
    }
        
}