#include <bits/stdc++.h> using namespace std; #define pb push_back #define eb emplace_back #define ll long long #define pii pair < int, int > #define fr first #define sc second #define mk make_pair #define sz(s) (int)s.size() #define all(s) s.begin(), s.end() #define ok puts("ok"); #define whatis(x) cerr << #x << " = " << x << endl; #define pause system("pause"); const int N = (int)3e4 + 7; const int inf = (int)1e9 + 7; vector < int > gr[N]; int n, m; int dist[N]; int bb[N]; int bfs() { set < pii > s; memset(dist, 63, sizeof dist); s.insert(mk(0, bb[1])); dist[bb[1]] = 0; while (!s.empty()) { pii v = *s.begin(); s.erase(s.begin()); if (v.sc == bb[2]) return v.fr; for (int i = 0; i < sz(gr[v.sc]); i++) { if (i < sz(gr[v.sc]) - 1 && gr[v.sc][i] == gr[v.sc][i + 1]) continue; int d = gr[v.sc][i]; for (int j = v.sc + d, k = 1; j <= n; j += d, k++) { if (v.fr + k < dist[j]) { s.erase(mk(dist[j], j)); dist[j] = v.fr + k; s.insert(mk(dist[j], j)); } if (binary_search(all(gr[j]), d)) break; } for (int j = v.sc - d, k = 1; j >= 1; j -= d, k++) { if (v.fr + k < dist[j]) { s.erase(mk(dist[j], j)); dist[j] = v.fr + k; s.insert(mk(dist[j], j)); } if (binary_search(all(gr[j]), d)) break; } } } return -1; } main() { scanf("%d %d", &n, &m); for (int i = 1; i <= m; i++) { int a, b; scanf("%d %d", &a, &b); a++; bb[i] = a; gr[a].pb(b); } for (int i = 1; i <= n; i++) { sort(all(gr[i])); } printf("%d", bfs()); }

skyscraper.cpp:59:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main() {
      ^
skyscraper.cpp: In function 'int main()':
skyscraper.cpp:60:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &n, &m);
   ~~~~~^~~~~~~~~~~~~~~~~
skyscraper.cpp:63:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &a, &b);
     ~~~~~^~~~~~~~~~~~~~~~~