P1531 I Hate It

#include <bits/stdc++.h>
using namespace std;
#define lc i<<1 
#define rc i<<1|1
const int N=2e5+5;
int n,m,a[N],ma[N<<2],x,y;
void up(int i){ma[i]=max(ma[lc],ma[rc]);
}
void build(int i,int l,int r){if(l==r)ma[i]=a[l];else{int mid=(l+r)>>1;build(lc,l,mid);build(rc,mid+1,r);up(i);}
}
int query(int i,int l,int r,int ql,int qr){if(ql<=l&&qr>=r)return ma[i];int mid=(l+r)>>1;int ans=INT_MIN;if(ql<=mid)ans=max(ans,query(lc,l,mid,ql,qr));if(qr>mid)ans=max(ans,query(rc,mid+1,r,ql,qr));return ans;
}
void update(int i,int l,int r,int x,int y){if(l==r){if(ma[i]<y)ma[i]=y;return;}int mid=(l+r)>>1;if(x<=mid)update(lc,l,mid,x,y);else update(rc,mid+1,r,x,y);up(i);
}
int main(){cin>>n>>m;for(int i=1;i<=n;i++)cin>>a[i];build(1,1,n);while(m--){char c;cin>>c>>x>>y;if(c=='Q'){cout<<query(1,1,n,x,y)<<endl;}else{update(1,1,n,x,y);}}return 0;
}