#include <bits/stdc++.h> using namespace std; typedef long long ll; typedef pair<int, int> pii; typedef pair<ll, ll> pll; const int MAXN = 2000; const ll INF = 1e12; int N, M, B[MAXN+10], P[MAXN+10]; ll dist[MAXN+10], adj[MAXN+10][MAXN+10]; struct Queue { int u; ll w; bool operator < (const Queue &p) const { return w>p.w; } }; int main() { int i, j; scanf("%d%d", &N, &M); for(i=1; i<=M; i++) scanf("%d%d", &B[i], &P[i]), B[i]++; for(i=1; i<=N; i++) for(j=1; j<=N; j++) adj[i][j]=INF; for(i=1; i<=M; i++) { for(j=1; B[i]+j*P[i]<=N; j++) adj[B[i]][B[i]+j*P[i]]=min(adj[B[i]][B[i]+j*P[i]], (ll)j); for(j=1; B[i]-j*P[i]>=1; j++) adj[B[i]][B[i]-j*P[i]]=min(adj[B[i]][B[i]-j*P[i]], (ll)j); } for(i=1; i<=N; i++) dist[i]=INF; priority_queue<Queue> PQ; PQ.push({B[1], 0}); while(!PQ.empty()) { Queue now=PQ.top(); PQ.pop(); if(dist[now.u]<=now.w) continue; dist[now.u]=now.w; for(i=1; i<=N; i++) if(adj[now.u][i]!=INF && dist[i]>now.w+adj[now.u][i]) PQ.push({i, now.w+adj[now.u][i]}); } if(dist[B[2]]==INF) dist[B[2]]=-1; printf("%lld", dist[B[2]]); }

skyscraper.cpp: In function 'int main()':
skyscraper.cpp:24:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &N, &M);
     ~~~~~^~~~~~~~~~~~~~~~
skyscraper.cpp:25:52: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for(i=1; i<=M; i++) scanf("%d%d", &B[i], &P[i]), B[i]++;
                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~