@[bfxbfx](/space/show?uid=152894) ……你在干吗
```
#include<iostream>//
#include<cstdio>
#include<cstring>
#include<string>
#include<iomanip>
#include<cmath>
using namespace std;
char z[101];
int main()
{
string x,y;
int i,s,t,n;
cin>>n>>x>>y;
for(i=0;i<=n-1;i++)
if(x[i]>y[i])
z[i]=y[i];
else if(x[i]<y[i]){cout<<"-1";goto se;}
else z[i]=y[i]+1;
for(i=0;i<=n-1;i++)
cout<<z[i];
se:return 0;
}
```
by shajjl @ 2018-12-16 09:54:08