include <stdio.h>

int main() {

int n;
scanf("%d", &n);

if (n < 100 || n > 999) {
    printf("None");
} else {
    int tam = 0;
    while (n > 0) {
        tam = tam * 10 + n % 10;
        n /= 10;
    }
    printf("%d", tam );
}
return 0;

}