#include <stdio.h>
#include <string.h>
#define NrCifMax 1009999
using namespace std;
int M[NrCifMax],N[NrCifMax],X[50];
long long D,x;

void GetN(int A[])
{
    char V[NrCifMax];
    fgets(V+1,NrCifMax,stdin);
    A[0]=strlen(V+1)-1;
    for(int i=1;i<=A[0];i++)A[A[0]+1-i]=(V[i]-'0');

}

void GetD()
{
    char V[50];
    fgets(V+1,NrCifMax,stdin);
    int l=strlen(V+1)-1;
    for(int i=1;i<=l;i++)D=D*10+(V[i]-'0');
}

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

void Adun(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;
}

int main()
{
    freopen("next.in", "r", stdin);
    freopen("next.out", "w", stdout);
    GetN(N);GetD();
    x=Mod(N,D);
    if(x)x=D-x;
    while(x)
    {
        X[++X[0]]=x % 10;
        x/=10;
    }
    Adun(N,X);
    for(int i=N[0];i>0;i--)printf("%d",N[i]);printf("\n");
    return 0;

}