#include<stdio.h>
#include<string.h>
#include<ctype.h>

int findLastWOrdLength(char*s)
{
    int len =strlen(s);
    if(len>0 && s[len-1]=='\n')
    {
        s[len-1]='\0';
        len--;
    }
    for(int i=0;i<len;i++)
    {
        if(!isalpha(s[i]) && s[i] != ' ')
        {
            return -1;
        }
    }
    while(len>0 && s[len-1] == ' ')
    {
        len--;
    }
    int lastWordLength =0;
    int i=len-1;
    while(i>=0 && s[i] != ' ')
    {
        lastWordLength++;
        i--
    }
    return lastWordLength;
}

int main()
{
    char s[21];
    fgets(s,sizeof,stdin);
    int result = findLastWordLength(s);
    if(result == -1)
    {
        printf("Invalid input \n");
    }
    else
    {
        printf("%d\n",result);
    }
return 0;
}