【Water Problem】A+B problem (High-precision)

The "A+B problem" is very easy,but I failed for many times.

The code:

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<string>
#include<queue>
#include<deque>
#include<stack>
#include<vector>
#include<algorithm>
#include<iomanip>
#define LL long long
#define MAXN 50001
#define P 123456
using namespace std;
int a[P],b[P],c[P],ka=1,kb=1;
char ca[P],cb[P];
int main()
{
    scanf("%s%s",ca,cb);
    int lena=strlen(ca),lenb=strlen(cb);
    int j=1;
    for(int i=lena-1;i>=0;i--)
    {
        a[ka]+=j*(ca[i]-'0');
        j*=10;
        if(j==1000)
            j=1,ka++;
    }
    
    if(j!=1)
        ka++,j=1;
    for(int i=lenb-1;i>=0;i--)
    {
        b[kb]+=j*(cb[i]-'0');
        j*=10;
        if(j==1000)
            j=1,kb++;
    }
    if(j!=1)
        kb++,j=1;
    
    //a[],b[] finish
    
    int e=0;
    for(int i=1;i<=max(ka,kb);i++)
    {
        c[i]=(a[i]+b[i]+e)%1000;
        e=(a[i]+b[i]+e)/1000;
    }
    int k=max(ka,kb)+1;
    while(k>0&&!c[k]) k--;
        printf("%d",c[k]);
    for(int i=k-1;i>=1;i--)
        printf("%03d",c[i]);
    
    return 0;
}

I have forgot to plus the "e" first, so I have so much mistake!!!