#include <algorithm>
#include <cstdio>

using namespace std;

const int N=1000005;

int a[N], b[N];
char cit[N];

void add(int A[], int B[])
{
      int i, t = 0;
      for (i=1; i<=A[0] || i<=B[0] || t; i++, t/=10)
              A[i] = (t += A[i] + B[i]) % 10;
      A[0] = i - 1;
}

long long mod(int A[], long long B)
{
      int i;
      long long t = 0;
      for (i = A[0]; i > 0; i--)
              t = (t * 10 + A[i]) % B;
      return t;
}

int main()
{
    freopen("next.in", "r", stdin);
    freopen("next.out", "w", stdout);
    long long d, r;
    int i;
    fgets(cit, N, stdin);
    for(i=0;cit[i]!='\n';i++) a[++a[0]]=cit[i]-'0';
    reverse(a+1, a+a[0]+1);
    scanf("%lld", &d);
    r=mod(a, d);
    if(r) r=d-r;
    while(r)
    {
        b[++b[0]]=r%10;
        r/=10;
    }
    add(a, b);
    for(i=a[0];i;i--) printf("%d", a[i]);
}