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

int main() {
    int n,i;
    char str[500];
    int evenSum = 0, oddSum = 0;
    
     scanf("%d", &n);
     getchar();
     
    fgets(str,sizeof(str),stdin);
    
    int count = 0;
    for (i = 0;str[i]!='\0'&& count < n; i++){
        
         if(str[i]=='')
         continue;
         
         if(!isalpha(ch)) {
            printf("invalid input");
            return 0;
         }
     
         if ((int)str[i] % 2 == 0)
            evenSum += (int)str[i];
         else
            oddSum += (int)str[i];
            
            
            count++;
    }
    
    if(count < n){
        printf("invalid input");
        return 0;
    }
    
    printf("%d", abs(evenSum - oddSum));
    return 0;
}