6 9 42

13

#include <stdio.h>


long convert(long v, int base)
{
    long ans, weight;
    int digit;

    ans = 0;
    weight = 1;
    while(v) 
   {
        digit = v % 10;
        v /= 10;
        if(digit >= base) 
	 {
            ans = -1;
            break;
        }
        ans += weight * digit;

        weight *= base;
    }

    return ans;
}

int main()
{
    long p, q, r;
    long p2, q2, r2;
    int ans=0;

    scanf("%ld%ld%ld", &p, &q, &r);
    
    for(int i=2; i<16; i++) 
   {
        p2 = convert(p, i);
      
        q2 = convert(q, i);
       
        r2 = convert(r, i); 

        if(p2 * q2 == r2) 
	{
            ans = i;
            break;
        }
    }

    printf("%d\n", ans);

    return 0;
}