This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
/*input
3 2
1 3
3 2
*/
#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<long long,null_type,less_equal<long long>,rb_tree_tag,tree_order_statistics_node_update> indexed_set;
#pragma GCC optimize("Ofast")
//#pragma GCC target("avx2")
//order_of_key #of elements less than x
// find_by_order kth element
using ll=long long;
using ld=long double;
using pii=pair<int,int>;
#define f first
#define s second
#define pb push_back
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(int i=1;i<=n;i++)
#define FILL(n,x) memset(n,x,sizeof(n))
#define ALL(_a) _a.begin(),_a.end()
#define sz(x) (int)x.size()
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()),c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
const ll maxn=5e5+5;
const ll maxlg=__lg(maxn)+2;
const ll INF64=4e18;
const int INF=0x3f3f3f3f;
const ll MOD=1e9+7;
const ld PI=acos(-1);
const ld eps=1e-6;
#define lowb(x) x&(-x)
#define MNTO(x,y) x=min(x,(__typeof__(x))y)
#define MXTO(x,y) x=max(x,(__typeof__(x))y)
template<typename T1,typename T2>
ostream& operator<<(ostream& out,pair<T1,T2> P){
out<<P.f<<' '<<P.s;
return out;
}
template<typename T>
ostream& operator<<(ostream& out,vector<T> V){
REP(i,sz(V)) out<<V[i]<<((i!=sz(V)-1)?" ":"");
return out;
}
ll mult(ll a,ll b){
return a*b%MOD;
}
ll mypow(ll a,ll b){
a%=MOD;
if(a==0) return 0;
if(b<=0) return 1;
ll res=1LL;
while(b){
if(b&1) res=(res*a)%MOD;
a=(a*a)%MOD;
b>>=1;
}
return res;
}
int dp[maxn][26];
int r1[maxn],r2[maxn];
int tot[26];
int main(){
int n,m;
cin>>n>>m;
REP1(i,n) r1[i]=r2[i]=i;
REP(i,m){
int a,b;
cin>>a>>b;
if(a<b){
MXTO(r1[a],b);
}
else{
MXTO(r2[b],a);
}
}
set<int> up,down;
REP1(i,n+1) up.insert(i),down.insert(i);
REP(i,26) tot[i]=1;
for(int i=n;i>=1;i--){
while((*up.lower_bound(i+1))<=r1[i]){
int tmp=(*up.lower_bound(i+1));
up.erase(tmp);
int pf=0;
REP(j,26){
tot[j]=(tot[j]-pf+MOD)%MOD;
pf=(pf+dp[tmp][j])%MOD;
}
}
while((*down.lower_bound(i+1))<=r2[i]){
int tmp=(*down.lower_bound(i+1));
down.erase(tmp);
int pf=0;
for(int j=25;j>=0;j--){
tot[j]=(tot[j]-pf+MOD)%MOD;
pf=(pf+dp[tmp][j])%MOD;
}
}
REP(j,26) dp[i][j]=tot[j];
int pf=0;
REP(j,26) pf=(pf+dp[i][j])%MOD;
REP(j,26) tot[j]=((tot[j]+pf)%MOD-dp[i][j]+MOD)%MOD;
}
int ans=0;
REP(i,26) ans+=dp[1][i],ans%=MOD;
cout<<ans<<'\n';
}
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