#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[100];
    int i;
    for(i=0;i<N;i++);
    {
        scanf(" %c",&arr[i]);
    }
    int evensum=0,oddsum=0;
    char*p=arr;
    for(i=0;i<N;i++;p++)
    {
        if(!isalpha(*p))
        {
            printf("Invalid input");
            return 0;
            
        }
        int val=(int)(*p);
        if(val%2==0)
              evensum+=val;
        else
              oddsum=+val;
    }
    int diff=evensum-oddsum;
    if(diff<0)diff=-diff;
    printf("%d",diff);
    return 0;
}