#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';
    
    for(i=0;s[i];i++){
        if(!isalpha(s[i]) && s[i]) != ' '){
            printf("Invalid input\n");
            return 0;
            
        }
    }
    for (i = len -1; 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;
      
}