C++ :

#include<iostream>
using namespace std;
int a[1000];
int main()
{
	int n;
	cin>>n;
	a[1]=1;
	a[2]=2;
	for(int i=3;i<=n;++i)
	a[i]=a[i-1]+a[i-2];
	cout<<a[n];
}

Pascal :

var n,i:longint;
    a:array[1..30] of longint;
begin
  readln(n);
  a[1]:=1;
  a[2]:=2;
  for i:=3 to n do
    a[i]:=a[i-1]+a[i-2];
  writeln(a[n]);
end.