24375번: ПОДНИЗ ↗

#include <bits/stdc++.h>

#define for1(s,n) for(int i = s; i < n; i++)
#define for1j(s,n) for(int j = s; j < n; j++)
#define foreach(k) for(auto i : k)
#define foreachj(k) for(auto j : k)
#define pb(a) push_back(a)
#define sz(a) a.size()

using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef vector <int> iv1;
typedef vector <vector<int> > iv2;
typedef vector <ll> llv1;
typedef unsigned int uint;
typedef vector <ull> ullv1;
typedef vector <vector <ull> > ullv2;

string a, b;

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	
	cin >> a >> b;
	
	sort(a.begin(), a.end());
	sort(b.begin(), b.end());
	
	int i = 0;
	int j = 0;
	
	while(i < a.length() && j < b.length()) {
		if(a[i] == b[j]) {
			cout << a[i];
			
			i++;
			j++;
		} else if(a[i] < b[j]) {
			i++;
		} else {
			j ++;
		}
	}	
}