#include <iostream>

using namespace std;
long long maxi,sum=1,sum1=1,n,a,b,i,v[100000],v1[100000];
int main()
{
    cin>>n>>a>>b;
    if(a>b)
        maxi=a;
    else
        maxi=b;
    v[maxi]=1;
    v1[maxi]=1;
    for(i=maxi+1;i<n+maxi;i++)
    {
        v[i]=sum1;
        v1[i]=sum;
        sum=sum+v[i]-v[i-a];
        sum1=sum1+v1[i]-v1[i-b];
    }
    cout<<sum+sum1;

    return 0;
}