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

int main(void) {
    int sum = 0;
    for (;;) {
        int ch = getchar();
        if (!isdigit((unsigned char)ch)) break; // leave loop with ENTER, EOF, 'a', ...
        sum += ch - '0';
    }
    printf("sum of digits is %d.\n", sum);
    return 0;
}