#include <cstdio>
#include <algorithm>

using namespace std;

const int I_MAX_CHANSONS = 100000;
const int INFINI = 1000*1000*1000;

int degreUtilisation[I_MAX_CHANSONS+1];
int nbUtilisesMax = -INFINI;

int main()
{
    int nbChansons;
    scanf("%d", &nbChansons);

    int iSeq = 1, nbUtilises = 0;

    for(int iChanson = 1 ; iChanson <= nbChansons ; iChanson++)
    {
        int curChanson;
        scanf("%d", &curChanson);

        if(curChanson == 0)
        {
            nbUtilises = 0;
            iSeq++;
        }
        else if(degreUtilisation[curChanson] != iSeq)
        {
            nbUtilises++;
            degreUtilisation[curChanson] = iSeq;
        }

        if(nbUtilises > nbUtilisesMax)
                nbUtilisesMax = nbUtilises;
    }

    printf("%d", nbUtilisesMax);
}