C :

#include<stdio.h>
int main()
{
	int a[50]={0};
	int b[50]={0};
	int c[50]={0};
	int n;
	scanf("%d",&n);
	a[0]=1;
	b[0]=1;
	int i,m;
		if(n==0)
	{
		printf("0\n");
	}
	else
	{
		if(n==1||n==2)
		{
			printf("1\n");
		}
		else
		{
			for(i=0;i<n-3;i++)
	   {
		for(m=0;m<50;m++)
		{
			c[m] = a[m] +b [m];
			if(c[m]>9)
			{
				c[m] = c[m] - 10;
				a[m+1] = a[m+1] + 1;
			}
		}
		for(m=0;m<50;m++)
		{
			a[m] = b[m];
			b[m] = c[m];
		}
	
		}
			for(i=0;;i++)
	{
		if(c[49-i]!=0)
		{
			break;
		}
	}
	for(m=49-i;m>-1;m--)
	{
		printf("%d",c[m]);
	}
	}
	}
	
	
	return 0;
}

C++ :

#include<iostream>
#include<cstdlib>
const int n=10000;
long long a[n];
using namespace std;
int main()
{
	int k;
	cin>>k;
	a[0]=0;
	a[1]=1;
	a[2]=1;
	for(int i=2;i<k;i++)
	  a[i]=a[i-1]+a[i-2];
	cout<<a[k-1];
	//system("pause");
	return 0;
}

Pascal :

var
   n,a,b,i,c:longint;
begin
 readln(n);
 a:=0;
 b:=1;
 for i:=3 to n do
  begin
   c:=b;
   b:=a+b;
   a:=c;
  end;
 writeln(b);
end.

Python :

# coding=utf-8
def fib(n):
    if n == 1:
        return 0
    if n == 2:
        return 1
    else:
        return fib(n-1) + fib(n-2)


import io
import sys
sys.stdout = io.TextIOWrapper(sys.stdout.buffer,encoding='utf8')
for line in sys.stdin:
    a = line.split()
    print(fib(int(a[0])))