C :

#include <stdio.h>

int a[1001] = {0,1,1};

int main(void) {
	int i, n;
	do
		scanf("%d", &n);
	while(!(n >= 1 && n <= 1000));
	for(i = 3; i <= n; i ++)
		a[i] = a[i-2] + a[i-1];
	printf("%d", a[n]);
	return 0;
}

C++ :

#include<cstdio>
using namespace std;
int a[110]; 
int main()
{
	int i,n;
	scanf("%d",&n);
	a[1]=1;
	a[2]=1;
	for(i=3;i<=n;i++)
	{
		a[i]=a[i-1]+a[i-2];
	}
	printf("%d\n",a[n]);
	return 0;
}

Pascal :

var i,j,k,m,n:longint;
  a:array[1..10000]of longint;
begin
  readln(n);
  a[1]:=1;
  a[2]:=1;
  for i:=3 to n do
    a[i]:=a[i-1]+a[i-2];
  write(a[n]);
end.