// editor1
#include<stdio.h>
#include<ctype.h>
int main()
{
    int n;
    scanf("%c",&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;
}