#include<bits/stdc++.h>

#define For(i,_beg,_end) for(int i=(_beg),i##end=(_end);i<=i##end;++i)
#define Rep(i,_beg,_end) for(int i=(_beg),i##end=(_end);i>=i##end;--i)

template<typename T>T Max(const T &x,const T &y){return x<y?y:x;}
template<typename T>T Min(const T &x,const T &y){return x<y?x:y;}
template<typename T>int chkmax(T &x,const T &y){return x<y?(x=y,1):0;}
template<typename T>int chkmin(T &x,const T &y){return x>y?(x=y,1):0;}
template<typename T>void read(T &x){
	T f=1;char ch=getchar();
	for(;ch<'0'||ch>'9';ch=getchar())if(ch=='-')f=-1;
	for(x=0;ch>='0'&&ch<='9';ch=getchar())x=x*10+ch-'0';
	x*=f;
}

typedef long long LL;
const int N=1010,mod=998244353;
int n,m;
LL a,b,p,q,dp[N][N],g[N][N],pw[N];
LL A[N],f[N<<1];

LL power(LL,LL);
LL Solve(int);

int main(){
	read(n);read(m);read(a);read(b);
	p=a*power(b,mod-2)%mod;q=(mod+1-p)%mod;
	pw[0]=1;
	For(i,1,m) pw[i]=pw[i-1]*p%mod;
	
	printf("%lld\n",(Solve(m)-Solve(m-1)+mod)%mod);
	return 0;
}

LL Solve(int k){
	memset(dp,0,sizeof dp);
	memset(g,0,sizeof g);
	For(i,1,k+2) g[0][i]=dp[0][i]=1;
	For(i,1,k) Rep(j,k/i+1,2){
		For(l,1,i) dp[i][j]=(dp[i][j]+g[l-1][j+1]*g[i-l][j]%mod*pw[l-1]%mod*q)%mod;
		g[i][j]=(g[i][j+1]*pw[i]+dp[i][j])%mod;
	}
	memset(A,0,sizeof A);
	For(i,0,k) A[i+1]=q*g[i][2]%mod*pw[i]%mod;
	memset(f,0,sizeof f);
	f[0]=1;
	For(i,1,k){
		f[i]=g[i][2]*pw[i]%mod;
		For(j,1,i) f[i]=(f[i]+A[j]*f[i-j])%mod;
	}
	k++;
	For(i,k,k<<1) For(j,1,k) f[i]=(f[i]+A[j]*f[i-j])%mod;
	if(n<=k)return f[n];
	int y=n-k,len=1,L=0;
	LL res[N<<2],tmp[N<<2],x[N<<2];
	memset(res,0,sizeof res);
	memset(x,0,sizeof x);
	res[0]=1;x[1]=1;
	for(;y;y>>=1){
		if(y&1){
			For(i,0,L+len) tmp[i]=0;
			For(i,0,L) For(j,0,len) tmp[i+j]=(tmp[i+j]+res[i]*x[j])%mod;
			L+=len;
			Rep(i,L,k) For(j,1,k) tmp[i-j]=(tmp[i-j]+tmp[i]*A[j])%mod;
			chkmin(L,k-1);
			For(i,0,L) res[i]=tmp[i];
		}
		For(i,0,len+len) tmp[i]=0;
		For(i,0,len) For(j,0,len) tmp[i+j]=(tmp[i+j]+x[i]*x[j])%mod;
		len<<=1;
		Rep(i,len,k) For(j,1,k) tmp[i-j]=(tmp[i-j]+tmp[i]*A[j])%mod;
		chkmin(len,k-1);
		For(i,0,len) x[i]=tmp[i];
	}
	LL ans=0;
	For(i,0,k-1) ans=(ans+res[i]*f[i+k])%mod;
	return ans;
}
LL power(LL x,LL y){
	LL res=1;
	for(;y;y>>=1,x=x*x%mod) if(y&1) res=res*x%mod;
	return res;
}