#include "bits/stdc++.h"
#define MAXN 100009
#define INF 998244353
#define mp(x,y) make_pair(x,y)
#define all(v) v.begin(),v.end()
#define pb(x) push_back(x)
#define wr cout<<"----------------"<<endl;
#define ppb() pop_back()
#define tr(ii,c) for(__typeof((c).begin()) ii=(c).begin();ii!=(c).end();ii++)
#define ff first
#define ss second
#define my_little_dodge 46
#define debug(x)  cerr<< #x <<" = "<< x<<endl;
using namespace std;

typedef long long ll;
typedef pair<int,int> PII;
template<class T>bool umin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool umax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
int mod(ll x){x%=INF;
	if(x<0)x+=INF;
	return x;	
}
const int N=1004;
char s[N],t[N];
int dp[N][N][26],n,m;
int rec(int x,int y,int last){
	if(x==n and y==m)return 1;
	int &ret=dp[x][y][last];
	if(~ret)return ret;ret=1;
	if(x<n and s[x]-'a'!=last)ret=mod(ret+rec(x+1,y,s[x]-'a'));
	if(y<m and t[y]-'a'!=last)ret=mod(ret+rec(x,y+1,t[y]-'a'));	
	return ret;
}
int main(){
    //freopen("file.in", "r", stdin);
    scanf("%s",s);n=strlen(s);
    scanf("%s",t);m=strlen(t);
    memset(dp,-1,sizeof dp);
    int ans=0;
    for(int i=0;i<n;i++)
    	for(int j=0;j<m;j++){
    		ans=mod(ans+rec(i+1,j,s[i]-'a'));
    		ans=mod(ans+rec(i,j+1,t[j]-'a'));
    	}
    for(int i=0;i<n;i++){
    	int l=i+1;	
    	while(l<n and s[l]!=s[l-1])l++;
    	ans=(ans-(l-i)*1LL*m);
    }
	for(int j=0;j<m;j++){
		int r=j+1;
		while(r<m and t[r]!=t[r-1])r++;
		ans=(ans-(r-j)*1LL*n);
	}	
    printf("%d\n",ans);
	return 0;
}
