This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define rng(i,x,n) for(int i=x;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define vec(...) vector<__VA_ARGS__>
#define _3x2WzQf ios::sync_with_stdio(0),cin.tie(0)
typedef long long ll;
using pii=pair<int,int>;
using vi=vector<int>;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}
// e
//snuke's mod int
template <ll mod>
struct modint{
ll x; // typedef long long ll;
modint(ll x=0):x((x%mod+mod)%mod){}
modint operator-()const{return modint(-x);}
modint& operator+=(const modint a){if((x+=a.x)>=mod) x-=mod; return *this;}
modint& operator-=(const modint a){if((x+=mod-a.x)>=mod) x-=mod; return *this;}
modint& operator*=(const modint a){(x*=a.x)%=mod; return *this;}
modint operator+(const modint a)const{modint res(*this); return res+=a;}
modint operator-(const modint a)const{modint res(*this); return res-=a;}
modint operator*(const modint a)const{modint res(*this); return res*=a;}
modint pow(ll n)const{
modint res=1,x(*this);
while(n){
if(n&1)res*=x;
x*=x;
n>>=1;
}
return res;
}
modint inv()const{return pow(mod-2);}
};
using mint=modint<1000'000'007>;
signed main(){
_3x2WzQf;
int n,m;
cin>>n>>m;
assert(n*n*27*27<=5e8);
vec(vi) qry(n,vi(2,-1));
rep(i,m){
int l,r;
cin>>l>>r;
l-=1,r-=1;
bool type=0;
if(l>r){
swap(l,r);
type=1;
}
qry[l][type]=max(qry[l][type],r);
}
vec(vec(vec(mint))) dp(n+1,vec(vec(mint))(27,vec(mint)(2))),ndp;
per(ch,26){
dp[n][ch][0]=1;
}
per(i,n-1){
ndp=vec(vec(vec(mint)))(n+1,vec(vec(mint))(27,vec(mint)(2)));
int r0=qry[i][0];
int r1=qry[i][1];
// print(r0,r1);
rng(j,i+1,n+1){
rep(x,26){
rep(y,26){
if(x==y) continue;
if(r0!=-1 and y>x) continue;
if(r1!=-1 and y<x) continue;
rep(t,2){
ndp[i][y][(y>x?1:0)]+=dp[j][x][t];
}
}
rep(t,2){
if(t==1 and j<r0){
continue;
}
if(t==0 and j<r1){
continue;
}
ndp[j][x][t]+=dp[j][x][t];
}
}
}
dp.swap(ndp);
}
mint ans=0;
rep(j,n+1){
rep(x,26){
rep(t,2){
ans+=dp[j][x][t];
}
}
}
print(ans.x);
//
return 0;
}
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