#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#include<cassert>
#include<random>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (int)(Y);++(X))
#define reps(X,S,Y) for (int (X) = (int)(S);(X) < (int)(Y);++(X))
#define rrep(X,Y) for (int (X) = (int)(Y)-1;(X) >=0;--(X))
#define rreps(X,S,Y) for (int (X) = (int)(Y)-1;(X) >= (int)(S);--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)),(X).end())
#define Endl endl
#define NL <<"\n"

using namespace std;
using ll=long long;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
template<class T> using vv=vector<vector<T>>;
template<class T> inline bool MX(T &l,const T &r){return l<r?l=r,1:0;}
template<class T> inline bool MN(T &l,const T &r){return l>r?l=r,1:0;}
//#undef NUIP
#ifdef NUIP
#include "benri.h"
#else
#define out(args...)
#endif
#ifdef __cpp_init_captures
template<typename T>vector<T> table(int n, T v){ return vector<T>(n, v);}
template <class... Args> auto table(int n, Args... args){auto val = table(args...); return vector<decltype(val)>(n, move(val));}
#endif
const ll MOD=1e9+7; //998244353

ll modpow_(ll r,ll n,ll m=MOD){
  ll re=1,d=r%m;
  if(n<0)(n%=m-1)+=m-1;
  for(;n;n/=2){
    if(n&1)(re*=d)%=m;
    (d*=d)%=m;
  }
  return re;
}
template <int mod=MOD> struct ModInt{
  int v;
  ModInt(int v=0):v(v){}
  ModInt operator+(const ModInt &n)const{return v+n.v<mod ? v+n.v : v+n.v-mod;}
  ModInt operator-(const ModInt &n)const{return v-n.v<0 ? v-n.v+mod : v-n.v;}
  ModInt operator*(const ModInt &n)const{return ll(v)*n.v%mod;}
  ModInt operator/(const ModInt &n)const{return ll(v)*modpow_(n.v%mod,-1,mod)%mod;}
  ModInt operator+(const ll &n)const{return v+n<mod ? v+n : v+n-mod;}
  ModInt operator-(const ll &n)const{return v-n<0 ? v-n+mod : v-n;}
  ModInt operator*(const ll &n)const{return ll(v)*(n%mod)%mod;}
  ModInt operator/(const ll &n)const{return ll(v)*modpow_(n%mod,-1,mod)%mod;}
  ModInt& operator+=(const ModInt &n){v+=n.v; if(v>=mod) v-=mod; return *this;}
  ModInt& operator-=(const ModInt &n){v-=n.v; if(v<0) v+=mod; return *this;}
  ModInt& operator*=(const ModInt &n){v=ll(v)*n.v%mod; return *this;}
  ModInt& operator/=(const ModInt &n){v=ll(v)*modpow_(n.v,-1,mod)%mod; return *this;}
  ModInt& operator+=(const ll &n){v+=n; if(v>=mod) v-=mod; return *this;}
  ModInt& operator-=(const ll &n){v-=n; if(v<0) v+=mod; return *this;}
  ModInt& operator*=(const ll &n){v=ll(v)*n%mod; return *this;}
  ModInt& operator/=(const ll &n){v=ll(v)*modpow_(n,-1,mod)%mod; return *this;}
	bool operator==(const ModInt &n)const{return v==n.v;};
	bool operator!=(const ModInt &n)const{return v!=n.v;};
	ModInt& operator++(){ return operator+=(1); }
	ModInt& operator--(){ return operator-=(1); }
	ModInt operator++(int i){ ModInt tmp(*this); operator++(); return tmp; }
	ModInt operator--(int i){ ModInt tmp(*this); operator--(); return tmp; }
};
#ifdef NUIP
class MINT_FRAC____{
public:
	unordered_map<int,pii> dict;
	MINT_FRAC____(int n){
		rep(p,n+1)reps(q,1,n+1)if(__gcd(p,q)==1){
			dict[1ll*p*modpow_(q,-1)%MOD]=pii(p,q);
			dict[MOD-1ll*p*modpow_(q,-1)%MOD]=pii(-p,q);
		}
	}
} Il1Il1Il1(1000);
template<int mod> ostream& operator<<(ostream &os,const ModInt<mod> &n){if(Il1Il1Il1.dict.count(n.v)) os<<n.v<<"("<<Il1Il1Il1.dict[n.v].X<<"/"<<Il1Il1Il1.dict[n.v].Y<<")";else os<<n.v;return os;};
#else
template<int mod> ostream& operator<<(ostream &os,const ModInt<mod> &n){return os<<n.v;};
#endif
template<int mod> ModInt<mod> operator+(const ll &n,const ModInt<mod> &m){return m.v+n<mod ? m.v+n : m.v+n-mod;}
template<int mod> ModInt<mod> operator-(const ll &n,const ModInt<mod> &m){return n-m.v<0 ? n-m.v+mod : n-m.v;}
template<int mod> ModInt<mod> operator*(const ll &n,const ModInt<mod> &m){return ll(m.v)*(n%mod)%mod;}
template<int mod> ModInt<mod> operator/(const ll &n,const ModInt<mod> &m){return ModInt<mod>(n%mod)/m;}
typedef ModInt<MOD> mint;
template <int mod> ModInt<mod> modpow(ModInt<mod> r,ll n){ ModInt<mod> re(1); if(n<0)(n%=mod-1)+=mod-1; for(;n;n/=2){if(n&1) re*=r; r*=r;} return re;}
vector<mint> fact,finv,inv;
mint comb(ll n,ll r){ if(n<r||r<0)return 0; return fact[n]*finv[n-r]*finv[r];}
class Doralion{
  void Modinvs(vector<mint> &re,int n){ re.resize(n+1); re[1]=1; for(int i=2;i<=n;++i)re[i]=re[MOD%i]*(MOD-MOD/i);}
  void Facts(vector<mint> &re,int n){ re.resize(n+1); re[0]=1; rep(i,n)re[i+1]=re[i]*(i+1);}
  void Factinvs(vector<mint> &re,const vector<mint> &inv,int n){ re.resize(n+1); re[0]=1; rep(i,n)re[i+1]=re[i]*inv[i+1];}
public:
  Doralion(int n){ Modinvs(inv,n); Facts(fact,n); Factinvs(finv,inv,n);}
} doralion(1123456);
using pmm=pair<mint,mint>;
mint modpow(ll r,ll n){ return modpow_(r,n);}

mint bf(int n,int a,int b){
	set<int> st{0};
	queue<int> que; que.emplace(0);
	const int A=(1<<a)-1;
	const int B=(1<<b)-1;
	while(que.size()){
		int x=que.front(); que.pop();
		rep(i,n-a+1){
			int y=x&~(A<<i);
			if(st.insert(y).Y) que.emplace(y);
		}
		rep(i,n-b+1){
			int y=x|(B<<i);
			if(st.insert(y).Y) que.emplace(y);
		}
	}
	// for(int x:st){rep(i,n) cout<<(x>>i&1); cout NL;}
	return st.size();
}

mint solve(int n,int a,int b){
	if(a>b) swap(a,b);
	vector<mint> el(n+1); //1 or long 0 only
	el[0]=1;
	rep(i,n){
		el[i+1]+=el[i];
		reps(d,a,n)if(i+d+1<=n) el[i+d+1]+=el[i];
	}
	vector<mint> step(n+1);
	rep(d,n+1){
		reps(s,1,a){
			int rem=d-(s+1);
			if(rem>=0 && rem+1<b) step[d]+=el[rem];
		}
	}
	// out(el,step,1);
	vector<mint> dp(n+1);
	rep(d,n+1){
		reps(s,1,a){
			int rem=d-(s+1);
			if(rem>=0 && rem<b) dp[d]+=el[rem];
		}
	}
	rep(i,n)reps(j,i+1,n+1) dp[j]+=dp[i]*step[j-i];
	vector<mint> last(n+1);
	rep(i,n+1)rep(j,n+1)if(i+j<=n){
		int len=i+1;
		if(j>=a) len+=j;
		if(len>=b) continue;
		// out(i,j,el[i],1);
		last[i+j]+=el[i];
	}
	mint re=0;
	rep(i,n+1)rep(j,n+1)if(i+j==n){
		int len=i;
		if(j>=a) len+=j;
		if(len>=b) continue;
		// out(i,j,el[i],1);
		re+=el[i];
	}
	reps(i,1,n+1){
		re+=dp[i]*last[n-i];
	}
	return modpow(2,n)-re;
}

int main(){
  ios_base::sync_with_stdio(false); cin.tie(0);
  cout<<fixed<<setprecision(0);
	if(0){
	reps(n,1,17)reps(a,1,n+1)reps(b,1,n+1){
		mint exp=bf(n,a,b);
		mint act=solve(n,a,b);
		if(exp!=act){
			out(exp,act,n,a,b,1);
			// exit(0);
		}
	}
	return 0;
	}
	int n,a,b;
	cin>>n>>a>>b;
	cout<<solve(n,a,b) NL;
  return 0;
}


Measured memory_bytes: 16272