#include <stdio.h>

int main() {
    char str[100];
    char *ptr;
    char min;
    
    scanf("%s", &str);
    
    ptr = str;
    min = *ptr;
    
    while (*ptr != '\0') {
        if (*ptr < min) {
            min = *ptr;
        }
        ptr++;
    }
    
    printf("%c", min);
    
    return 0;
}