Aceasta este soluția oficială a problemei:
#include <iostream>
using namespace std;
long long n,b,r,k,x,s,i,nr ;
int main()
{
cin >> n >> b >> r ;
// numarul cifrelor lui r
k = 0 ;
x = r ;
while ( x != 0 )
{
k++ ;
x = x / 10 ;
}
// afisare
if ( k > n ) cout << -1 ;
else if ( k == n ) cout << r ;
else
{
s = 1 ;
for ( i = 2 ; i <= n ; i++ ) s = ( s * 10 ) % b ;
if ( s <= r ) nr = r - s ;
else nr = b - s + r ;
if ( nr == 0 )
{
cout << 1 ;
for ( i=1 ; i<=n-1 ; i++ ) cout << 0 ;
}
else
{
k = 0 ;
x = nr ;
while ( x != 0 )
{
k++ ;
x = x / 10 ;
}
cout << 1 ;
for ( i=1 ; i<=n-k-1 ; i++ ) cout << 0 ;
cout << nr ;
}
}
return 0;
}
