#include <vector>
#include <string>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <bitset>
#include <stack>
#include <list>
#include <numeric>
#include <algorithm>
#include <random>
#include <chrono>
#include <cstdio>
#include <fstream>
#include <iostream>
#include <sstream>
#include <iomanip>
#include <climits>
#include <cctype>
#include <cmath>
#include <ctime>
#include <cassert>
using namespace std;
#define ULL unsigned long long
#define LL long long
#define PII pair <int, int>
#define VB vector <bool>
#define VI vector <int>
#define VLL vector <LL>
#define VD vector <double>
#define VS vector <string>
#define VPII vector <pair <int, int> >
#define VVI vector < VI >
#define VVB vector < VB >
#define SI set < int >
#define USI unordered_set <int>
#define MII map <int, int>
#define UMII unordered_map <int, int>
#define MS multiset
#define US unordered_set
#define UM unordered_map
#define UMS unordered_multiset
#define UMM unordered_multimap
#define FORN(i, n) for(int i = 0; i < (n); ++i)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define MX(x, y) x = max(x, y);
#define MN(x, y) x = min(x, y);
#define SZ size()
#define BG begin()
#define EN end()
#define CL clear()
#define X first
#define Y second
#define RS resize
#define PB push_back
#define MP make_pair
#define ALL(x) x.begin(), x.end()
#define INS insert
#define ER erase
#define CNT count
template <class T> ostream& operator <<(ostream & os, const vector<T> &vec)
{
for (int i = 0; i < vec.size() - 1; ++i) os << vec[i] << ' ';
return os << vec[vec.size() - 1];
}
template <class T1, class T2> ostream& operator <<(ostream & os, const pair<T1, T2> &p)
{
return os << p.X << " " << p.Y;
}
template <typename T>
void pr(T var1)
{
cout << var1 << '\n';
}
template <typename T, typename... Types>
void pr(T var1, Types... var2)
{
cout << var1;
pr(var2...);
}
void in(int &n, VI &a) //array of ints
{
cin >> n;
a.CL, a.RS(n + 1);
FOR(i, 1, n) cin >> a[i];
}
void in(int &n, VS &a) //array of strings
{
cin >> n;
a.CL, a.RS(n + 1);
FOR(i, 1, n) cin >> a[i];
}
void in(int &n, VPII &a) //array of pairs
{
cin >> n;
a.CL, a.RS(n + 1);
FOR(i, 1, n) cin >> a[i].X >> a[i].Y;
}
void in(int &n, int &m, VVI &g) //unweighted graph
{
cin >> n >> m;
g.CL, g.RS(n + 1);
FOR(i, 1, n)
{
int x, y;
cin >> x >> y;
g[x].PB(y);
g[y].PB(x);
}
}
void in(int &n, VVI &g) //unweighted tree
{
cin >> n;
g.CL, g.RS(n + 1);
FOR(i, 1, n - 1)
{
int x, y;
cin >> x >> y;
g[x].PB(y);
g[y].PB(x);
}
}
void in(int &n, int &m, vector <VPII> &g) //weighted graph
{
cin >> n >> m;
g.CL, g.RS(n + 1);
FOR(i, 1, n)
{
int x, y, z;
cin >> x >> y >> z;
g[x].PB({y, z});
g[y].PB({x, z});
}
}
void in(int &n, vector <VPII> &g) //weighted tree
{
cin >> n;
g.CL, g.RS(n + 1);
FOR(i, 1, n - 1)
{
int x, y, z;
cin >> x >> y >> z;
g[x].PB({y, z});
g[y].PB({x, z});
}
}
int n, nn, q, leaves;
VI a, tree, lazy;
void propagate(int node)
{
lazy[node * 2] += lazy[node];
lazy[node * 2 + 1] += lazy[node];
lazy[node] = 0;
}
void update(int node, int left, int right, int l, int r, int delta)
{
if (l <= left and right <= r)
{
lazy[node] += delta;
return;
}
propagate(node);
int mid = (left + right) / 2;
if (l <= mid) update(node * 2, left, mid, l, r, delta);
if (mid + 1 <= r) update(node * 2 + 1, mid + 1, right, l, r, delta);
tree[node] = max(tree[node * 2] + lazy[node * 2],
tree[node * 2 + 1] + lazy[node * 2 + 1]);
}
int main()
{
#ifdef AT_HOME
freopen("a.in", "r", stdin);
freopen("a.out", "w", stdout);
#endif
ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
cin >> nn >> q;
n = (1 << nn) - 1;
leaves = n - n / 2;
a.RS(n + 1, 1);
tree.RS(2 * n), lazy.RS(2 * n);
update(1, 1, leaves, 1, leaves, nn - 1);
FOR(i, 1, q)
{
int node, cost;
cin >> node >> cost;
int delta = cost - a[node];
a[node] = cost;
int l, r;
l = r = node;
while (l <= n / 2) l *= 2, r = r * 2 + 1;
l -= n / 2, r -= n / 2;
update(1, 1, leaves, l, r, delta);
pr(tree[1] + lazy[1]);
while(node)
node /= 2;
}
return 0;
}