#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define plx pair<ll,int>
#define f first
#define s second
#define pb push_back
#define all(x) x.begin(),x.end()
#define vi vector<int>
#define vvi vector<vi>
#define pp pair<ll,int>
#define ub(x,i) upper_bound(all(x),i)-x.begin()
using namespace std;
const int mxn=5e5+5,inf=1e9+7;
vector<int>up[mxn],dw[mxn];
ll dp[mxn][27]{0};
ll pu[27]{0},pd[27]{0};
multiset<int>um,dm;
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int n,m;cin>>n>>m;
for(int i=1;i<=m;i++){
int a,b;cin>>a>>b;
if(a<b)up[a].pb(b);
else dw[b].pb(a);
}
for(int i=1;i<=26;i++)dp[n][i]=1;
for(int i=n-1;i>=1;i--){
um.insert(i+1);dm.insert(i+1);
for(int j=1;j<=26;j++)pu[j]+=dp[i+1][j],pd[j]+=dp[i+1][j],pu[j]%=inf,pd[j]%=inf;
for(auto r : up[i]){
while(!um.empty()&&*um.begin()<=r){
for(int j=1;j<=26;j++)pu[j]-=dp[*um.begin()][j],pu[j]%=inf;
um.erase(um.begin());
}
}
for(auto r : dw[i]){
while(!dm.empty()&&*dm.begin()<=r){
for(int j=1;j<=26;j++)pd[j]-=dp[*dm.begin()][j],pd[j]%=inf;
dm.erase(dm.begin());
}
}
ll u=0;
for(int j=26;j>=1;j--){
dp[i][j]=u+1;
u+=pu[j];u%=inf;
}u=0;
for(int j=1;j<=26;j++){
dp[i][j]+=u;dp[i][j]%=inf;
u+=pd[j];u%=inf;
}
}ll ans=0;
for(int i=1;i<=26;i++)ans+=dp[1][i],ans%=inf;
cout<<(ans%inf+inf)%inf;
}
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |