// editor2
#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main ()
{
    char s[25];
    if(!sets(s, sizeof s, stdin))return 0;
    int len = strlen(s);
    if (s[len-1]=="\n") s[--len]="\0";
    
    for (int i=0;i<len;i++)
    if (!isalpha(s[i]) && !isspace(s[i]))
    return printf ("Invalid input\n"),0;
    
    int i=len-1,lastLen=0;
    while(i>=0&& isspace(a[i])) i--;
    while(i>=0&& isalpha(a[i])) lastLen++,i--;
    
    printf("%d\n", lastLen);
}