//C语言 递归法
#include<stdio.h>
int fab(int);

int main()
{
    int k1, k2;
    scanf("%d%d", &k1,& k2);
    int sum = 0;
    for (int i = k1; i <= k2; i++)
    {
        sum = sum + fab(i);
    }
    printf("%d", sum);
    
    return 0;
}

int fab(int n)
{
    if (n == 1 || n == 2)
        return 1;
    else
        return fab(n - 1) + fab(n - 2);
}

#include<bits/stdc++.h>
using namespace std;
int a[10005];
int main()
{
    int x,y,sum=0;
    cin>>x>>y;
    for(int i=1;i<=y;i++)
        cin>>a[i];
    a[1]=1;
    a[2]=1;
    for(int i=3;i<=y;i++)
        a[i]=a[i-2]+a[i-1];
    for(int i=x;i<=y;i++)
        sum+=a[i];
    cout<<sum<<endl;
    return 0;
} 

#include<stdio.h>
int Fibonacci(int K);
int main()
{
    int k1, k2;
    int s1, s2, s3;
    int sum = 0;
    int num;
    scanf("%d", &k1);
    scanf("%d", &k2);
    if (k1 > k2)
    {
        return -1;
    }
    if (k1 == 1)
    {
        s1 = 1;
        s2 = 0;
    }
    else if (k1 == 2)
    {
        s1 = 0;
        s2 = 1;
    }
    else
    {
        s1 = Fibonacci(k1 - 2);
        s2 = Fibonacci(k1 - 1);
    }
    
    
    for (int i = k1; i <= k2; i++)
    {
        num = s1 + s2;
        sum = sum + num;
        s3 = s2;
        s2 = s1 + s2;
        s1 = s3;
    }
    printf("%d", sum);
    return 0;
}
//非递归做法
int Fibonacci(int K)
{
    int a1 = 1;
    int a2 = 1;
    int a3, an;

    if (K <= 0)
    {
        return -1;
    }
    if (K == 1 || K == 2)
    {
        return 1;
    }
    for (int i = 0; i < K-2; i++)
    {
        an = a1 + a2;
        a3 = a2;
        a2 = a1 + a2;
        a1 = a3;
    }
    return an;
}

/*
// 递归做法
int Fibonacci(int K)
{
    if (K == 2 || K == 1)
    {
        return 1;
    }
    else
    {
        return Fibonacci(K - 1)+Fibonacci(K - 2);
    }
}
*/