Codeforces Round ＃392 (Div. 2) D. Ability To Convert

#include<bits/stdc++.h>

using namespace std;

#define X first
#define Y second
#define eps 1e-2
#define gcd __gcd
#define pb push_back
#define PI acos(-1.0)
#define lowbit(x) (x)&(-x)
#define bug printf("!!!!!\n");
#define mem(x,y) memset(x,y,sizeof(x))

#define int long long 

typedef long long LL;
typedef long double LD;
typedef pair<int,int> pii;
typedef unsigned long long uLL;

const int maxn = 1e5+2;
const int INF  = 1<<30;
const int mod  = 1e9+7;

int n;string s;

void solve(){
    
    cin>>n>>s;
    int st,ed=s.size()-1;
    LL ans=0,mul=1;
    while(ed>=0){
    
        int tmp=0;
        for(int i=0;i<=ed;i++){
    
            if(ed-i>15) continue;
            tmp=0;
            for(int j=i;j<=ed;j++)
                tmp=tmp*10+s[j]-'0';
            if(tmp<n){
    st=i;break;}
        }
        while(st<ed&&s[st]=='0') ++st;
        ans=ans+mul*tmp;mul=mul*n;ed=st-1;
    }
    cout<<ans<<endl;
    
    return;
}

int32_t main()
{
    
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
// ios::sync_with_stdio(false);
    int t = 1;
    //scanf("%d",&t);
    while(t--){
    
    // printf("Case %d: ",cas++);
        solve();
    }
    return 0;
}