Increasing Array.cpp

#include<bits/stdc++.h>
using namespace std;
#define INF 2147483647
#define INFL 9223372036854775807
#define pii pair<int,int>
#define F first
#define S second
#define mp make_pair
#define pb push_back
#define ll long long
#define ull unsigned long long
#define M 1000000007
#define FASTIO ios_base::sync_with_stdio(false);cin.tie(NULL); cout.tie(NULL);
#define take(x) scanf("%d",&x)
#define DE(x) printf("\ndebug %d\n",x);
#define vout(x) for(int i=0;i<x.size();i++) printf("%d ",x[i]);
#define pie acos(-1)
#define MOD 998244353

int main(){
    int t = 1;
    FASTIO;
    //scanf("%d",&t);
    for(int tc=1;tc<=t;tc++){
        int n;
        cin>>n;
        int ara[n];
        for(int i=0;i<n;i++){
            cin>>ara[i];
        }
        ll res = 0;
        for(int i=1;i<n;i++){
            if( ara[i]<ara[i-1] ){
                res+=ara[i-1]-ara[i];
                ara[i] = ara[i-1];
            }
        }
        cout<<res;
    }
}