#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define Max 10
#define Num(x) (isdigit(x)?x-'0':x-'a'+10) //hodnota znaku
#define N(x) (m=Num(x),max=max>m?max:m,m)  //nejvetsi znak

char a[Max],b[Max],c[Max];

int main(void)
{
 int z,m,max=0;
 scanf("%s%s%s",&a,&b,&c);
 strrev(a);strrev(b);strrev(c); //obrat retezce

 for(int i=0; i<strlen(c); i++)
   if (z = N(a[i]) + N(b[i]) - N(c[i])) {printf("%d\n",z);return;}

 printf("%d\n",max+1);
 return 0;
}