#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>
int main(){
    int n;
    char arr[100];
    int evenSum = 0,oddsum = 0;
    scanf("%d",&n);
    if(n < 1 || n > 100){
        printf("Invalid input\n");
        return 0;
    }
    for(int i=0;i<n;i++){
        scanf("%c",&arr[i]);
        if(!isalpha(arr[i]))
        {
            printf("Invalid input\n");
            return 0;
        }
    }
    char *ptr = arr;
    for(int i - 0;i < n;i++){
        int ascii = (int)*(ptr + i);
        if(ascii % 2 == 0)
            evenSum += ascii;
        else
            oddSum += ascii;
    }
    printf("%d\n",abs(evenSum));
    return 0;
}