#include<iostream>
#include <cstring>
using namespace std;
void reverse(char *s) {
    int len = strlen(s);
    char c;
    for(int i=0;i<len/2;i++){
        c = *(s+i);
        *(s+i) = *(s+len-i-1);
        *(s+len-i-1) = c;
    }
    *(s+len) = '\0';
}