#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;
}