U_can_say_11.c

#include <stdio.h>
#include <string.h>
int main(int argc, const char * argv[])
{
    char num[1010] = {0};
    
    while(scanf("%s",num)!=EOF){
        if(strcmp(num, "0") == 0){
            break;
        }
        size_t len = strlen(num);
        int c;
        int odd = 0;
        int even = 0;
        int res;
        for(c=0;c<len;c++){
            if(c%2 == 0){
                even += num[c]-'0';
            }else{
                odd +=num[c]-'0';
            }
        }
        
        if(even > odd){
            res = (even-odd)%11;;
        }else{
            res = (odd-even)%11;;
        }
        
        if(res == 0){
            printf("%s is a multiple of 11.\n",num);
        }else{
            printf("%s is not a multiple of 11.\n",num);
        }
    }
    return 0;
}