#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(!salpha(*(ptr + i)))
        {
            printf("Invalid input");
        return 0;
        }
    if(*(ptr + i) %2 ==0)
    evenSum += *(ptr + i);
    else 
    oddsum += *(ptr + 1);
    }
    int diff = evenSum - oddSum;
    if(diff < 0) diff = -diff;
    printf("%d",diff);
    return 0;
}