#include #include #include #include #include #include #include #include #include static const int MOD = 1000000007; using ll = long long; using u32 = unsigned; using u64 = unsigned long long; using namespace std; template constexpr T INF = ::numeric_limits::max()/32*15+208; int main() { int n, m; cin >> n >> m; vector t(m+1), p(m+1); for (int i = 0; i < m; ++i) { scanf("%lld %lld", &t[i], &p[i]); } for (int i = 0; i < m; ++i) { if(t[i+1]-t[i] < abs(p[i]-p[i-1])){ puts("No"); return 0; } } puts("Yes"); return 0; }