// editor2
#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main() {
    char s[25];
    int valid =1;
    fgets(s, sizeof(s), stdin);
    s[strcspn(s, "\n")] = "\0";
    int len = strlen(s);
    int count = 0;
    for (int i =0; i < len ; i++) {
    if (!isalpha(s[i] && s[i] != ' ' ) {
        Valid = 0;
        break;
    }
}
if (!isValid) {
    printf("-1\n");
} else {
    int lastWordLength = 0;
    int i = len - 1;
    while (i >=0 && s[i] == ' ') {
        i--;
    }
         while (i >=0 && s[i] != ' ') {
         lastWordLength++;
        i--;
    }
    printf("%d\n",lastWordLength);
}
return 0;
}