/**
* Author: Sergey Kopeliovich (Burunduk30@gmail.com)
*/
#include <bits/stdc++.h>
using namespace std;
#define forn(i, n) for (int i = 0; i < (int)(n); i++)
typedef long long ll;
int main() {
ios_base::sync_with_stdio(0), cin.tie(0);
int n;
cin >> n;
int x[n], y[n];
forn(i, n) {
cin >> x[i] >> y[i];
}
ll s = 0;
forn(i, n) {
int j = (i + 1) % n;
s += x[i] * y[j] - x[j] * y[i];
}
if (s < 0) {
reverse(x, x + n);
reverse(y, y + n);
}
forn(i, n) {
int j = (i + 1) % n;
int k = (i + 2) % n;
if ((x[k] - x[i]) * (y[j] - y[i]) - (x[j] - x[i]) * (y[k] - y[i]) > 0) {
puts("NO");
return 0;
}
}
puts("YES");
return 0;
}