#include <iostream>
#include <string.h>

using namespace std;

int main()
{
    char s[256];
    int i = 0;
    cin.getline(s, 256);
    int a,b,f;
    f = 1;
    a = 0;
    b = strlen(s) - 1;
    while ( a < b ){
        while (s[b] == ' ' ){
            b = b - 1;
        }
        while (s[a] == ' '){
            a = a + 1;
        }
        if ( s[a] != s[b] ){
            f = 0;
            cout << a << " " << b << endl;
        }
        a = a + 1;
        b = b - 1;
    }
    if ( f == 1){
        cout << "yes";
    }else
        cout << "no";
}