九度OJ 1015 还是A+B

#include<stdio.h>
#include<math.h>
int main(int argc, char *argv[])
{
    int a,b,k;
    int i;
    int ak,bk;
    long num;
    while(~scanf("%d%d%d",&a,&b,&k))
    {
        if(a==0&&b==0)return 0;
        num=pow(10,k);
        if(a%num==b%num)
            printf("-1\n");
        else
            printf("%d\n",a+b);
    }
    return 0;
}
 
/**************************************************************
    Problem: 1015
    User: kirchhoff
    Language: C
    Result: Accepted
    Time:0 ms
    Memory:1004 kb
****************************************************************/