[daily question in summer] function of rogu p3742 UMI

Topic link ：P3742 umi Function of - Luogu | New ecology of computer science education (luogu.com.cn)

Background

umi Found a mysterious function f.

Title Description

This function accepts two strings s1,s2. These strings can only be composed of lowercase letters , And have the same length . The output of this function is another length and s1,s2 The same string g.g Of the i Characters equal to s1 Of the i Characters and s2 Of the i Minimum of characters , Simply speaking ,g[i]=min(s1[i],s2[i]).

for example ：f("ab","ba")= "aa", f("nzwzl","zizez")="niwel".

She now has two strings of the same length with only lowercase letters x,y. Find any satisfaction f(x,z)=y Of

character string z. If you can't find such a string , Please export -1.

Input format

The first line gives the length of the following two strings n.

The second line gives a string x.

The third line gives a string y.

Output format

The first line outputs a string , Represents the qualified string you find . If you can't find it , Please export -1.

Examples #1

The sample input #1

2
ab
aa

Sample output #1

ba

Examples #2

The sample input #2

5
nzwzl
niwel

Sample output #2

xiyez

Examples #3

The sample input #3

2
ab
ba

Sample output #3

-1

Tips

about 100% The data of ,1<=n<=100.

AC code:

#include<iostream>

using namespace std;

int main()
{
	int l;
	cin>>l; 
	string s1,s2;
	cin>>s1>>s2;
	for(int i=0;i<l;i++)
	{
		if(s2[i]>s1[i])
		{
		    cout<<-1;
		    return 0;
		}
	}
	cout<<s2;
	
	return 0;
}