C++ code :
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll ;
int main() {
string a,b;
cin>>a>>b ;
map <char,ll> kk ;
ll n = b.size();
ll i = 0 ;
while(i<n){
char g = b[i];
kk[g]++;
i++;
}
n = a.size();
i = 0 ;
while(i<n){
char g = a[i];
if(kk[g]==0){
cout<<g ;
}
i++;
}
return 0;
}