https://codeforces.com/contest/1175/problem/B
题解:栈+模拟+标记
1、用栈记录for嵌套;
2、变量now记录当前栈内乘积;
3、当now大于的不再向栈内添加;
4、出栈时判断当前for是否在栈内;
5、ans大于时打标记;
/*
*@Author: STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const ll M=(1ll<<32)-1;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
ll ans,cnt,flag,temp,sum;
int vis[N];
char str[10];
struct node{};
int main()
{
#ifdef DEBUG
freopen("input.in", "r", stdin);
//freopen("output.out", "w", stdout);
#endif
//ios::sync_with_stdio(false);
//cin.tie(0);
//cout.tie(0);
//scanf("%d",&t);
//while(t--){
scanf("%d",&n);
stack<int>st;
temp=1;
while(n--){
cin>>str;
if(str[0]=='f'){
scanf("%d",&m);
if(flag){
continue;
}
st.push(m);
if(temp<=M)
vis[st.size()]=1,temp*=m;
}else if(str[0]=='e'){
if(flag){
continue;
}
m=st.top();
if(vis[st.size()])
vis[st.size()]=0,temp/=m;
st.pop();
}else{
ans+=temp;
if(ans>M)flag=1;
if(flag){
continue;
}
}
}
if(!flag)cout<<ans<<endl;
else cout<<"OVERFLOW!!!"<<endl;
//}
#ifdef DEBUG
printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
//cout << "Hello world!" << endl;
return 0;
}