#include <bits/stdc++.h> using namespace std; int N; int M; int l[500100]; int g[500100]; long long int mod = 1'000'000'007; struct node{ int s,e,m; bool lazy[2]; long long int v[2][30]; node *l,*r; node(int S, int E){ s = S; e = E; m = (s + e)/2; lazy[0] = false; lazy[1] = false; if(s != e){ l = new node(s,m); r = new node(m + 1, e); } } void update(int i, vector<int> k){ if(s == e){ v[0][0] = 0; v[1][27] = 0; for(int j = 1; j <= 26; j++) v[0][j] = (v[0][j - 1] + k[j] + 1) % mod; for(int j = 26; j >= 1; j--) v[1][j] = (v[1][j + 1] + k[j] + 1) % mod; return; } if(i <= m) l -> update(i,k); else r -> update(i,k); for(int i = 0; i <= 27; i++){ v[0][i] = ((l -> v[0][i]) + (r -> v[0][i]))%mod; v[1][i] = ((l -> v[1][i]) + (r -> v[1][i]))%mod; } } void updatel(int S, int E, bool flag){ if(lazy[flag]) return; if(S <= s && e <= E){ if(lazy[flag]) return; lazy[flag] = true; for(int i = 0; i <= 27; i++){ v[flag][i] = 0; } return; } if(S <= m){ l -> updatel(S,E,flag); } if(m < E){ r -> updatel(S,E,flag); } for(int i = 0; i <= 27; i++){ v[flag][i] = ((l -> v[flag][i]) + (r -> v[flag][i]))%mod; } } vector<int> query(int S, bool lazy0, bool lazy1){ lazy0 |= lazy[0]; lazy1 |= lazy[1]; if(S <= s){ vector<int> temp = {0}; for(int i = 1; i <= 26; i++){ temp.push_back((v[0][i - 1] * (1-lazy0) + v[1][i + 1] * (1-lazy1)) % mod); } return temp; } if(S <= m){ vector<int> temp = r -> query(S,lazy0,lazy1); vector<int> temp1 = l -> query(S,lazy0,lazy1); for(int i = 0; i < temp.size(); i++){ temp[i] = (temp[i] + temp1[i]) % mod; } return temp; } else return r -> query(S,lazy0,lazy1); } }*root; int main(){ //while(true){ scanf(" %d",&N); scanf(" %d",&M); for(int i = 0; i < N; i++){ l[i] = i - 1; g[i] = i - 1; } for(int i = 0; i < M; i++){ int u, v; scanf(" %d",&u); scanf(" %d",&v); if(u > v){ l[v] = max(l[v],u); } else{ g[u] = max(g[u],v); } } root = new node(1,N); vector<int> v = {0}; for(int i = 1; i <= 26; i++) v.push_back(0); root -> update(N,v); for(int i = N - 1; i >= 1; i--){ if(g[i] != i - 1) root -> updatel(i + 1,g[i],0); if(l[i] != i - 1) root -> updatel(i + 1,l[i],1); if(i == 1) break; root -> update(i,root -> query(i + 1,false,false)); } vector<int> b = root -> query(2,false,false); long long int ans = 0; for(int i : b){ ans += i; //printf("%d ",i); } //printf("\n"); ans = (ans + 26) % mod; printf("%lld\n",ans); //} } /* 10 8 2 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 */

misspelling.cpp: In function 'int main()':
misspelling.cpp:110:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  110 |         scanf(" %d",&N);
      |         ~~~~~^~~~~~~~~~
misspelling.cpp:111:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  111 |         scanf(" %d",&M);
      |         ~~~~~^~~~~~~~~~
misspelling.cpp:121:22: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  121 |                 scanf(" %d",&u);
      |                 ~~~~~^~~~~~~~~~
misspelling.cpp:122:22: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  122 |                 scanf(" %d",&v);
      |                 ~~~~~^~~~~~~~~~