# include <iostream>
# include <fstream>

using namespace std;

int ld( int d, int n )
{
    return ( n / d ) * d;
}

int main()
{
    ifstream fin( "pascal.in" );
    ofstream fout( "pascal.out" );

    int r, d, i, s;

    fin >> r >> d;

    i = d;
    while ( i <= ld( i, r ) && r - ld( i, r ) == ld( i, r ) )
        i *= d;
    i /= d;

    fout << ld( i, r ) - i;

    fin.close();
    fout.close();

    return 0;
}