#include <iostream>

using namespace std;

int main()
{
    int a[1000];
    int n=0,s,sx=0,m=0;
    cin >> n;
    for(int i=0;i<n;i++){
        cin >> a[i];
    }
    for(int u=1;u<n-1;u++){
            s=a[u]+a[u+1]+a[u+2];
            if(s>sx){
                sx=s;
                m=u+1;
            }}
    if (n==3){
        sx=a[0]+a[1]+a[2];
        m=2;
    }
    cout << sx << " " << m << endl;
}

#include<iostream>

using namespace std;

int main()
{
    int numSection;
    cin >> numSection;
    int a[numSection];
    for (int i = 0; i < numSection; i++)
    {
        cin >> a[i];
    }
    int n = numSection - 3 + 1;
    int max = 0;
    int middleNumSec = 0;
    for (int i = 0; i < n; i++)
    {
        if (i + 3 > numSection)
        {
            break;
        }
        int sum = 0;
        for (int j = i; j < i + 3; j++)
        {
            sum += a[j];
        }
        if (sum > max)
        {
            max = sum;
            middleNumSec = i + 2;
        }
    }
    cout << max << " " << middleNumSec << endl;

    system("pause");
    return 0;
}

My solution:
#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <queue>
#include <map>
#include <stack>
#include <algorithm>
#include <bitset>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <cstdio>
#include <iomanip>

#define F first
#define S second
#define ll long long
#define len length()
#define sqr(x) x*x
#define pb push_back
#define mp make_pair
#define sz(x) ((int) (x).size())
#define all(x) x.begin(), x.end()
#define allr(x) x.rbegin(), x.rend()
#define bp(x) __builtin_popcount(x)
#define INF numeric_limits<long long int>::max()
#define frp freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
#define forit(it, s) for(__typeof(s.begin()) it = s.begin(); it != s.end(); it++)

const int maxn = (int)1e6;
const int mod = (int)1e9 + 7;

using namespace std;

int n;
int a[maxn];
int sum,ans;
int cnt;

main(){
    scanf("%d",&n);
    for(int i=1; i <= n; i++){
        scanf("%d",&a[i]);
    }
    for(int i=1; i <= n-2; i++){
        sum=a[i]+a[i+1]+a[i+2];
        if(ans < sum){
            ans=sum;
            cnt=i+1;
        }
    }
    printf("%d %d",ans,cnt);


    return 0;
}

OMG man, thank u) this is correctly
#include <iostream>

using namespace std;

int a[1000], n = 0, s, sx = 0, m = 0;
void main()
{


    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    for (int u = 0; u < n; u++) {
        s = a[u] + a[u + 1] + a[u + 2];
        if (s > sx) {
            sx = s;
            m = u + 2;
        }
    }