// editor1
#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 es=0,os=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)
        es+=(ptr+i);
        else
        os+= *(ptr+i);
    }
    int diff=es-os;
    if(diff<0) diff=-diff;
    printf("%d",diff);
    return 0;
    
}