#include <cstdio>
#include <cstring>
#include <iostream>
#include <stack>
#define INF 2000100
using namespace std;
int map[1001][1001]; //0可以 1不可以
int num[1002],dp[1002];
int col[1002]={0};
int n;
int min(int a,int b)
{return a>b?b:a;
}
stack<int> s1;
stack<int> s2;
int main()
{scanf("%d",&n);for(int i=1;i<=n;++i)scanf("%d",&num[i]);num[n+1]=INF;dp[n+1]=INF;for (int i=n;i>=1;--i) dp[i]=min(dp[i+1],num[i]);for (int i=1;i<n;++i)for (int j=i+1;j<=n;++j)if (num[i]<num[j]&&num[i]>dp[j+1])map[i][j]=map[j][i]=1;for (int i=1;i<=n;++i){if (col[i]==0){col[i]=1;for (int j=i+1;j<=n;j++){if (map[i][j]&&col[j]==1){cout<<"0"<<endl;return 0;}else if (map[i][j]) col[j]=2;}}if (col[i]==2){for (int j=i+1;j<=n;j++){if (map[i][j]&&col[j]==2){cout<<"0"<<endl;return 0;} }}}int aim=1;for (int i=1;i<=n;i++){if (col[i]==1){cout<<"a ";s1.push(num[i]);}if (col[i]==2){cout<<"c ";s2.push(num[i]);}while (!s1.empty()){if (s1.top()==aim){aim++;cout<<"b ";s1.pop();}else break;}while (!s2.empty()){if (s2.top()==aim){aim++;cout<<"d ";s2.pop();}else break;}}while (!s1.empty()||!s2.empty()){    while (!s1.empty()){if (s1.top()==aim){aim++;cout<<"b ";s1.pop();}else break;}while (!s2.empty()){if (s2.top()==aim){aim++;cout<<"d ";s2.pop();}else break;}}cout<<endl;
}#include <cstdio>
#include <cstring>
#include <iostream>
#include <stack>
#include <cstdlib>
#define INF 2000100
using namespace std;
int map[1001][1001]; //0可以 1不可以
int num[1002],dp[1002];
int col[1002]={0};
int n;
int min(int a,int b)
{return a>b?b:a;
}
void  dfs(int x, int c)
{col[x] = c;for (int i=1;i<=n;++i)if (map[x][i]){if (col[i]==c){cout<<"0"<<endl;exit(0);}if (!col[i])dfs(i, 3-c);}
}stack<int> s1;
stack<int> s2;
int main()
{scanf("%d",&n);for(int i=1;i<=n;++i)scanf("%d",&num[i]);num[n+1]=INF;dp[n+1]=INF;for (int i=n;i>=1;--i) dp[i]=min(dp[i+1],num[i]);for (int i=1;i<n;++i)for (int j=i+1;j<=n;++j)if (num[i]<num[j]&&num[i]>dp[j+1])map[i][j]=map[j][i]=1;for (int i = 1; i <= n;++i)  if (!col[i]) dfs(i,1);int aim=1;for (int i=1;i<=n;i++){if (col[i]==1){cout<<"a ";s1.push(num[i]);}else {cout<<"c ";s2.push(num[i]);}while (!s1.empty()){if (s1.top()==aim){aim++;cout<<"b ";s1.pop();}else break;}while (!s2.empty()){if (s2.top()==aim){aim++;cout<<"d ";s2.pop();}else break;}}while (!s1.empty()||!s2.empty()){    while (!s1.empty()){if (s1.top()==aim){aim++;cout<<"b ";s1.pop();}else break;}while (!s2.empty()){if (s2.top()==aim){aim++;cout<<"d ";s2.pop();}else break;}}cout<<endl;
}