https://blog.csdn.net/lucky52529/article/details/89155694

#include <iostream>
using namespace std;

const int N = 1e5 + 10;
int st[N], top = -1;

inline push(int x){
    st[++top] = x;
}

int main(){
    int n;
    scanf("%d", &n);
    for(int i = 0; i < n; i++){
        int x;
        scanf("%d", &x);
        while(~top && st[top] >= x) top--;
        if(~top) printf("%d ", st[top]);
        else printf("-1 ");
        push(x);
    }
    return 0;
}