#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main()
{
    char s[21];
    if(scanf("%20[^\n]",s) != 1)
    {
        printf("invalid input.\n");
        return 1;
    }
    int len=strlen(s);
    int lastworldlength = 0;
    int i =len-1;
    while (i>=0 && s[i]=='')
    {
        if (!isalnum(s[i]))
        {
            printf("invalid input.\n");
            return 1;
        }
        lastworldlength++;
        i--;
    }
    printf("%d\n", lastworldlength);
    return 0;
}