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

int main(){
    char s[21];
    fgets(s, sizeof(s), stdin);
    s[strcspn(s, "\n")] = 0;
    
    int len_s = strlen(s);
    if (len_s <= 1 || len_s > 20){
        print("Invalid input\n");
        return 0;
    }
    
    for (int i = 0; i < len_s; i++){
        if(!isalpha(s[i]) && s[i] != ' '){
            printf("Invalid input\n");
            return 0;
        } 
    }
    
    int len = 0;
    for(int i = len_s - 1; i >= 0; i--){
        if (s[i] == ' ') break;
        len++;
    }
    
    printf("%d\n",len);
    return 0;
}