#include<stdio.h>
int main(){
    int n;
    scanf("%d",&n);
    if(n<0){
        printf("Invalid input");
        return 0;
    }
    char arr[10];
    int i;
    char*ptr=arr;
    for(i=0;i<n;i++){
        scanf("%c",arr[i]);
        if(!isalpha(arr[i])){
            printf("Invalid input");
            return 0;
        }
    }
    int evensum=0,oddsum=0;
    for(i=0;i<n;i++){
        int ascii=*(ptr+i);
        if(ascii%2==0)
        evensum+=ascii;
        else
        oddsum+=ascii;
    }
    int diff=evensum-oddsum;
    if(diff<0)diff=-diff;
    printf("%d",diff);
    return 0;
}