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 int long long
const int MOD = 1e9+7;
int n,m;
int dp[500005][30];
vector<pair<int,int>> qrysle[500005];
vector<pair<int,int>> secv[2];
signed main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    cin>>n>>m;
    int a,b;
    for(int i=1;i<=m;i++)
    {
        cin>>a>>b;
        if(a==b)
            continue;
        if(a<b)
        {
            qrysle[a+1].push_back({b,0});
            secv[0].push_back({a+1,b});
        }
        else
        {
            swap(a,b);
            qrysle[a+1].push_back({b,1});
            secv[1].push_back({a+1,b});
        }
    }
    for(int c=0;c<26;c++)
        dp[1][c]=1;
    int rez=26;
    for(int i=2;i<=n;i++)
    {
        for(int c=0;c<26;c++)
        {
            int p0=1,p1=1;
            for(auto x:secv[0])
                if(x.first<=i && x.second>=i)
                    p0 = max(p0, x.first);
            for(auto x:secv[1])
                if(x.first<=i && x.second>=i)
                    p1 = max(p1, x.first);
            for(int x=p1;x<i;x++)
                for(int u=c+1;u<26;u++)
                    dp[i][c] += dp[x][u];
            for(int x=p0;x<i;x++)
                for(int u=0;u<c;u++)
                    dp[i][c] += dp[x][u];
            dp[i][c]%=MOD;
            rez = (rez + dp[i][c])%MOD;
        }
    }
    cout<<rez;
    return 0;
}
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