Water trap

#include <iostream>
using namespace std;

int n, a[100001];
int maxime_st[100001];
int maxime_dr[100001];

int main(){
    cin >> n;
    int maxim = 0;
    for(int i = 1; i <= n; ++i){
        cin >> a[i];
        if(a[i] > maxim)
            maxim = a[i];
        maxime_st[i] = maxim;
    }

    maxim = 0;
    for(int i = n; i >= 1; --i){
        if(a[i] > maxim)
            maxim = a[i];
        maxime_dr[i] = maxim;
    }

    int w = 0;

    for(int i = 2; i < n; ++i)
        if(a[i] < min(maxime_st[i],maxime_dr[i])){
        w += (min(maxime_st[i],maxime_dr[i]) - a[i]);
        a[i] = min(maxime_st[i],maxime_dr[i]);
       }

    cout << w;
    return 0;
}