#include<bits/stdc++.h>
using ll = int_fast64_t;

int main(){
    int n;
    scanf("%d", &n);
    ll a[n];
    for(int i=0; i<n; i++){
        scanf("%ld", &a[i]);
        a[i] %= 10;
    }

    ll dp[1+n][10];
    for(int i=0; i<=n; i++) for(int j=0; j<10; j++) dp[i][j] = -1;
    dp[0][0] = 0;
    for(int i=0; i<n; i++){
        for(int j=0; j<10; j++){
            if(dp[i][j]<0) continue;
            dp[i+1][j] = std::max(dp[i+1][j], dp[i][j]);
            dp[i+1][(j+a[i])%10] = std::max(dp[i+1][(j+a[i])%10], dp[i][j]+1);
        }
    }
    printf("%ld\n", dp[n][0]);
    return 0;
}