Getting WA on 4th case on submission

help
1

I got the point that i need to get the set of char that appear only one time in one string of given set of string ,here is my code what could i possible be missing that i am not able to solve it.

#define ll long long
#define f(end) for(int i=0;i<end;i++)
#define e '\n'
#include <bits/stdc++.h>
using namespace std;

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int t=1,n;
// 	cin>>t;
	while(t--)
	{
	    cin>>n;
	    int temp=0;
	    string s,demo;
	    map<char,int> mp;
	    f(n){
	        cin>>s;
	        for(int j=0;j<s.length();j++){
	            if(mp[s[j]]<=temp) mp[s[j]]++;
	        }
	        temp++;
	    }
	   string ans="";
	   for(auto it:mp){
	       if(it.second==n) ans+=it.first;
	   }
	   if(ans=="") cout<<"no such string"<<e;
	   else cout<<ans<<e;
	}
	return 0;
}