Program to find nth Fibonacci number

Fibonacci number in mathematics is defined as the sum of the two previous elements in the series. Formally this is represented as 
f(n) = f(n-1) + f(n-2) where f(1) = 1 and f(2) = 1.

In this post we will see how to generate nth fibonacci number. The algorithm is self-explanatory from the program itself. So jumping in to the code directly..

#include <iostream>
using namespace std;
int fib(int n)
if( n < 3)
return 1;

int a = 1;
int b = 1;
int c = a+b;

int i = 3;
while ( i < n)
//store sum of two previous values in c
c = a + b;
a = b; //b is first and
b = c; //c is second for next iteration

return c;
int main()
int n;
cout<<fib(n)<<" ";
return 0;

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