POJ 1769 minimizing maximizer single-point update segment tree

POJ 1769//sep9 #include <iostream> using namespace std;
const int maxn=100012;
const int maxx=9999999;
int n,m;

int minv[maxn*4];
	void build (int l,int r,int k) {Minv[k]=maxx;  
    if (l==r) return; 
    int m= (L+R)/2;  
    Build (L,m,2*k);    
Build (m+1,r,2*k+1);
	} void Update (int i,int v,int k,int l,int R) {if (minv[k]>v) minv[k]=v;
	if (l==r) {return;
	} int m= (L+R)/2;;
	if (i<=m) update (I,V,2*K,L,M);
else update (I,V,2*K+1,M+1,R);
	} int query (int from,int to,int k,int l,int R) {if (from<=l&&r<=to) return minv[k];
	int m= (L+R)/2;;
	if (to<=m) return query (FROM,TO,2*K,L,M);
	else if (from>m) return query (FROM,TO,2*K+1,M+1,R);
else return min (query (from,to,2*k,l,m), query (From,to,2*k+1,m+1,r));
	} int main () {scanf ("%d%d", &n,&m);
	Build (1,n,1);
	Update (1,0,1,1,N);
		while (m--) {int s,t;
		scanf ("%d%d", &s,&t);
		if (s>=t) continue; int end=n;//n = t-1,t,... n all acceptable int v=query (s, end,1,1,n);		
	Update (T,V+1,1,1,N);		
} printf ("%d\n", Query (N,n,1,1,n)); }