#include<stdio.h>
#include<string.h>
long long b,c;
int d[17];
char a[1000000010];

long long mo()
{
    long long rez=0;
    for (int i=a[0];i>=1;--i)
        rez=(rez*10+a[i])%b;
    return rez;
}

void adun()
{
    long long carry=0;
    for(int i=1;i<=a[0];++i)
    {
        long long x=a[i]+c+carry;
        a[i]=x%10;
        carry=x/10;
        c=c/10;
    }
}

void afisare()
{
    for(int i=a[0];i>=1;--i)
        printf("%d",a[i]);
}

int main()
{
    freopen("next.in","r",stdin);
    freopen("next.out","w",stdout);
    scanf("%s",a+1);
    a[0]=strlen(a+1);
    if(a[0]%2==1)
    {
        a[a[0]/2+1]=a[a[0]/2+1]-'0';
    }
    for(int i=1;i<=a[0]/2;++i)
    {
        int x=a[i]-'0';
        a[i]=a[a[0]+1-i]-'0';
        a[a[0]+1-i]=x;
    }
    scanf("%lld",&b);
    c=mo();

    if(c==0)
    {
        afisare();
        return 0;
    }
    else
    {
        c=b-c;
        adun();
        afisare();
        return 0;
    }
}