#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;
}