Elevator Trouble

input/code.cpp: In function 'int main()':
input/code.cpp:27:17: warning: iteration 1000000u invokes undefined behavior [-Waggressive-loop-optimizations]
         dp[i]=-1;
                 ^
input/code.cpp:26:5: note: containing loop
     for(int i=0; i<1000001; i++)
     ^

#include <iostream>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <unordered_set>
#include <stdio.h>
#include <string.h>
#include <unordered_map>
#include <fstream>
#include <set>
#include <map>

#define MOD 1000000007
#define ll long long
#define N 1000000
#define float double

using namespace std;

int dp[1000000];

int main(){
    for(int i=0; i<1000001; i++)
        dp[i]=-1;
    int f,s,g,u,d;
    cin>>f>>s>>g>>u>>d;
    s--;
    g--;

    dp[s]=0;

    queue<int> j;
    j.push(s);
    while(j.size()){
        int a=j.front();
        j.pop();

        if(a+u<f&&dp[a+u]==-1){
            dp[a+u]=dp[a]+1;
            j.push(a+u);
        }

        if(a-d>0&&dp[a-d]==-1){
            dp[a-u]=dp[a]+1;
            j.push(a-u);
        }
    }

    if(dp[g]==-1)
        cout<<"use the stairs\n";
    else
        cout<<dp[g]<<endl;
    return 0;
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: TIME LIMIT EXCEEDED

Test 8

Verdict: TIME LIMIT EXCEEDED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: TIME LIMIT EXCEEDED

Test 12

Verdict: ACCEPTED