C - Great wall Bsearch

#include<stdio.h>
#include<queue>
using namespace std;
typedef long long int ll;
int main()
{
    int n,w;
    ll k;
    scanf("%d %d %d",&n,&w,&k);
    ll arr[n+1];
    ll maxh = 1;
    for(int i = 1 ; i <= n ; i ++){
        scanf("%lld",&arr[i]);
        if(maxh < arr[i])maxh = arr[i];
    }
    ll l = 0 , r = maxh;
    ll ans = maxh;
    while(l <= r){
        ll m = (l+r)/2;
        queue<pair<int,ll> > q;
        ll sumnow = 0;
        ll cnt = 0;
    //  printf("Test m %lld\n",m);
        for(int i = 1 ; i <= n && cnt <= k; i ++){
            if(!q.empty()){
                if(q.front().first+w == i){
                    sumnow -= q.front().second;
                    q.pop();
                }
            }
            if(arr[i]-sumnow > m){ //need to destroy
                ll dest = (arr[i]-sumnow)-m;
            //  printf("Destroy %d %lld \n",i,dest);
                sumnow += dest;
                cnt += dest;
                q.push({i,dest});
            }
        }
        if(cnt <= k){
            ans = m;
            r = m - 1;
        }
        else{
            l = m + 1;
        }
    }
    printf("%lld",ans);
    return 0;
}