#include <stdio.h>

int main() {
    int m, reversed = 0;
    scanf("%d", &m);

    if (m < 0) {
        printf("error");
    } else {
        while (m > 0) {
            reversed = reversed * 10 + m % 10;
            m /= 10;
        }
        printf("%d", reversed);
    }

    return 0;
}