#include<stdio.h>
#include<ctype.h>
int main(){
   int N;
   scanf("%d",&N);
   if(N<=0 || N>100)
   {
       printf("Invalid input");
       return 0;
   }
   char arr[N];
   for(int i=0; i<N; i++)
   {
       scanf(" %c",arr[i]);
   }
   int evenSum = 0, oddSum =0;
   char *ptr = arr;
   for(int i=0;i<N;i++)
   {
       if(!isalpha(*(ptr + i)))
       {
           printf("Invalid input");
           return 0;
       }
       if(*(ptr + i) %2 ==0)
       evenSum += *(ptr  + i);
       else
       oddSum += *(ptr + i);
   }
   int diff = evenSum - oddSum;
   if(diff < 0) diff = -diff;
   printf("%d",diff);
   return 0;
}