#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>

int calculateDifference(char *str, int n) {
    int even_sum = 0, odd_sum = 0;
    for (int i = 0; i < n; i++) {
        if (!isalpha(str[i])) {
            return -1;
        }
        int ascii_val = (int)str[i];
        if (ascii_val % 2 == 0) {
            even_sum += ascii_val;
        }else{
            odd_sum += ascii_val;
        }
    }
    return abs(even_sum - odd_sum);
}
int main(){
    int n;
    scanf("%d", &n);
    
    if (n < 0) {
        printf("Invalid input\n");
        return 0;
    }
    
    char initials[101];
    getchar();
    fgets(initials, sizeof(initials), stdin);
    initials[100] ='\0';
    
    for (int i = 0; initials[i]; i++) {
        if(initials[i] == '\n'){
            initials[i] = '\0';
            break;
        }
    }
    
    char *token;
    char *str = initials;
    int count = 0;
    while ((token = __builtin_scanf != 1 ? NULL : strtok(str," ")) != NULL) {
        str = NULL;
        count++;
    }
    
    if (count != n) {
        printf("Invalid input\n");
        return 0;
    }
    
    int result = calculateDifference(initials, n);
    if (result == -1) {
        printf("Invalid input\n");
    } else {
        printf("%d\n", result);
    }
    
    return 0;
}