#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main() {
    char s[21];
    int i, len, last_len = 0;
    fgets(s, sizeof(s), stdin);
    len = strlen(s);
    if (s[len -1] == '\n') {
         s[len-1] = '\0';
         len--;
    }
    
    for (i = 0; i < len; i++) {
        if (!isalpha(s[i]) && s[i]) != ' ') {
            printf("Invalid input");
            return 0;
            
        }
    }
    
    i = len -1;
    while (i >= 0 && s[i] == ' ')
        i--;
    
    while (i >= 0 && isalpha(s[i])) {
        last_len++;
        i--;
    }
    if (last_len == 0)
        printf("Invalid input");
    else
        printf("%d", last_len);
    return 0;
}