#include<cstdio>
#include<cstring>
#include<cstdlib>

struct Node{
 char member[3][21];
}teamSet[20];
int n;
unsigned int graph[21][21];
unsigned int teams[20];

unsigned int isOk(int I, int J){
   int i = 0;
   int j = 0;
   unsigned int flag = 0;
   for(i = 0; i < 3 && !flag; i++){
      for(j = 0; j < 3; j++){
         if(!strcmp(teamSet[I].member[i], teamSet[J].member[j])){
            flag = 1;
            break;
         }
      }
   }

   return flag;
}

int Check(unsigned int team){
   unsigned int c = 0;
   unsigned int tempSet = 0;
   int nCount = 0;
   int num = n;
   int isValid = 1;
   c = 0x00020000;
   while(num++ < 18){
      c >>= 1;
   }
   for(num = n; c > 0; c >>= 1, num--){
      if(c&team){
         nCount++;
         if(tempSet&c){
            isValid = 0;
            break;
         }
         tempSet |= teams[n - num + 1];
      }
   }

   return (1 == isValid) ? nCount : -1;
}

int main(int argc, char* argv[], char* env[])
{
   int i = 0;
   int j = 0;
   int t = 0;
   int maxTeams = 0;
   unsigned int c = 0;
   unsigned int tempN = 0;
   while(scanf("%d", &n) != EOF){
      for(i = 1; i <= n; i++){
         scanf("%s%s%s", teamSet[i].member[0], 
         teamSet[i].member[1], teamSet[i].member[2]);
      }
      for(i = 1; i <= n; i++){
         graph[i][i] = 0;
         for(j = i + 1; j <= n; j++){
            graph[i][j] = graph[j][i] = isOk(i, j);
         }
      }
      for(i = 1; i <= n; i++){
         teams[i] = graph[i][j];;
         for(j = 2; j <= n; j++){
            teams[i] <<= 1;
            teams[i] |= graph[i][j];
         }
      }
      maxTeams = 0;
      tempN = 1 << n;
      for(c = 1; c < tempN; c++){
         t = Check(c);
         if(t > maxTeams){
            maxTeams = t;
         }
      }
      printf("%d\n", maxTeams);
   }
   return 0;
}