#include <stdio.h>
#include <string.h>
int f(char*a){
    int length = strlen(a);
    int n=0;
    for (int i=0;i<length-1;i++){
        int left=a[i]-'0';
        int right=a[length-1]-'0';

        if((left%2==0&&right%2==0)||(left%2==1&&right%2==1)){ n++;}
    }
    return n;
}
int main() {
    char a[1000000];
    int n;
    scanf("%s",a);
    n=f(a);
    printf("%d",n);
    return 0;
}

求简化,这里直接判断个位了,免去相加