代码：

#include <iostream>
#include <algorithm>
#include <string.h>using namespace std;const int N = 100010;int h[N], hp[N], ph[N], cnt;void heap_swap(int a, int b)
{swap(ph[hp[a]] ,ph[hp[b]]);swap(hp[a], hp[b]);swap(h[a], h[b]);
}void down(int u)
{int t = u;if(u * 2 <= cnt && h[u * 2] < h[t]) t = u * 2;if(u * 2 + 1 <= cnt && h[u * 2 + 1] < h[t]) t = u * 2 + 1;if(u != t){heap_swap(u, t);down(t);}
}void up(int u)
{while(u / 2 && h[u] < h[u / 2]){heap_swap(u, u / 2);u >>= 1;}
}int main()
{int n, m = 0;scanf("%d", &n);while(n--){char op[5];int k, x;scanf("%s", op);if(!strcmp(op, "I")){scanf("%d", &x);cnt++;m++;ph[m] = cnt, hp[cnt] = m;h[cnt] = x;up(cnt);}else if(!strcmp(op, "PM")) printf("%d\n", h[1]);else if(!strcmp(op, "DM")){heap_swap(1, cnt);cnt--;down(1);}else if(!strcmp(op, "D")){scanf("%d", &k);k = ph[k];heap_swap(k, cnt);cnt--;down(k);up(k);}else {scanf("%d%d", &k, &x);k = ph[k];h[k] = x;down(k);up(k);}}return 0;
}