题解 | #还是A+B#

#include <iostream>
using namespace std;

bool is_equal(int a,int b,int k){
    int t=1;
    while(t<=k){
        t++;
        int aa=a%10;
        a/=10;
        int bb=b%10;
        b/=10;
        if(aa!=bb) return false;
    }
    return true;
}

int main() {
    int a,b,k;
    while(cin>>a>>b>>k){
        if(a==0&&b==0) break;
        if(is_equal(a,b,k)) cout<<-1<<endl;
        else cout<<a+b<<endl;
    }
    return 0;
}