#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 - oddsum));

return 0;
}