#include<stdio.h>

int main() {
    char s[105], out[105];
    scanf("%s", s);
    
    int j = 0;
    for (int i = 0; s[i]; i += 2) {
        int x = (s[i]-'0')*10 +
(s[i+1]-'0');
         if(len % 2!=0){
         printf("Invalid Input");
         return 0;
}
}
         if (x < 65 || x > 90) {
             
             printf("Invalid Input");
             return 0;
         }
         out[j++] = x;
    }
    out[j] = '\0';
    printf("%s", out);
}