Codeforces 455A dynamic programming

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algorithm

C++14

Guys I am new to competitive programming I was solving a problemhttps://codeforces.com/problemset/problem/455/A ,I took a solution and try it to understand it ,i get that well but i have a small doubt

#include<bits/stdc++.h>
    using namespace std;
    #define MAX 100005
    long long dp[100005];
        long long count1[100005];
        int main(){
        int n,x;
        cin>>n;
        for(int i=0;i<n;i++){
            cin >> x;
            count1[x]++;
           // res=max(res,x);
        }
        dp[0]=0;
        dp[1]=count1[1];
        for(int i=2;i<MAX;i++){
            dp[i]=max(dp[i-1],dp[i-2]+i*count1[i]);
        }
        cout<<dp[MAX-1];
    }

What I have tried:

BUT AS YOU CAN SEE THAT THE LOOP IS RUNNING MAX(100005) EVEN FOR SMALL TEST CASES ,WHEN I TRY TO OPTIMIZE THAT I CAME UP WITH THE SOLUTION

#include<bits/stdc++.h>
using namespace std;

int main(){
    long long dp[100005];
    long long count1[100005];
    int n;
    cin>>n;

    int x;
    int res=-100000;

    for(int i=0;i<n;i++){
        cin >> x;
        count1[x]++;
        res=max(res,x);
    }

    dp[0]=0;
    dp[1]=count1[1];

    for(int i=2;i<=res;i++){
        dp[i]=max(dp[i-1],dp[i-2]+i*count1[i]);
    }

    cout<< dp[res];


}

BUT THIS IS GIVING WRONG ANSWER ON TEST CASE 12 https://codeforces.com/contest/455/submission/47841668

Can anyone tell me where i did the mistake ? Why that competitive programmer that kind of mistake is that normal?