Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	io := NewIo()
	defer io.Flush()
	for {
		n := io.NextInt()
		if n == 0 {
			break
		}
		s := make([]string, n)
		for i := 0; i < n; i++ {
			s[i] = io.NextLine()
		}
		w := [5]int{5, 7, 5, 7, 7}
		ans := 0
	OUTER:
		for i := 0; i < n; i++ {
			cnt, wc := 0, 0
			for j := i; j < n; j++ {
				wc += len(s[j])
				if wc == w[cnt] {
					cnt++
					wc = 0
					if cnt == 5 {
						ans = i + 1
						break OUTER
					}
				} else if wc > w[cnt] {
					break
				}
			}
		}
		io.Println(ans)
	}
}

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := make([]interface{}, 0, len(a))
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := make([]interface{}, 0, len(a))
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define P pair<ll,ll>
#define FOR(I,A,B) for(ll I = (A); I < (B); ++I)
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin()) //ai>=v  x is sorted
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin()) //ai>v  x is sorted
#define NUM(x,v) (POSU(x,v)-POSL(x,v))  //x is sorted
#define SORT(x) (sort(x.begin(),x.end())) // 0 2 2 3 4 5 8 9
#define REV(x) (reverse(x.begin(),x.end())) //reverse
#define TO(x,t,f) ((x)?(t):(f))
#define CLR(mat) memset(mat, 0, sizeof(mat))
#define FILV(x,a) fill(x.begin(),x.end(),a)
#define FILA(ar,N,a) fill(ar,ar+N,a)
#define NEXTP(x) next_permutation(x.begin(),x.end())
ll gcd(ll a,ll b){if(a<b)swap(a,b);if(a%b==0)return b;else return gcd(b,a%b);}
ll lcm(ll a,ll b){ll c=gcd(a,b);return ((a/c)*(b/c)*c);}//saisyo kobaisu
#define pb push_back
#define pri(aa) cout<<(aa)<<endl
#define mp(x,y) make_pair(x,y)
#define fi first
#define se second
const ll INF=1e9+7;
const ll N = 1007;





int main(){
	while(1){
		ll n;cin>>n;
		if(n==0)break;
		ll wa=0;
		string s;
		vector<ll> len;
		FOR(i,0,n){
			cin>>s;
			len.pb(s.size());
		}
		ll ans=0;
		FOR(i,0,n){
			vector<ll> v;
			v.pb(0);
			if(ans!=0)break;
			FOR(j,i,n){
				if(v.size()==1){
					if(v[0]+len[j]>5)break;
					else if(v[0]+len[j]<5){
						v[0]+=len[j];
					}else{
						v[0]=5;
						v.pb(0);
					}
				}else if(v.size()==2){
					if(v[1]+len[j]>7)break;
					else if(v[1]+len[j]<7){
						v[1]+=len[j];
					}else{
						v[1]=7;
						v.pb(0);
					}
				}else if(v.size()==3){
					if(v[2]+len[j]>5)break;
					else if(v[2]+len[j]<5){
						v[2]+=len[j];
					}else{
						v[2]=5;
						v.pb(0);
					}
				}else if(v.size()==4){
					if(v[3]+len[j]>7)break;
					else if(v[3]+len[j]<7){
						v[3]+=len[j];
					}else{
						v[3]=7;
						v.pb(0);
					}
				}else if(v.size()==5){
					if(v[4]+len[j]>7)break;
					else if(v[4]+len[j]<7){
						v[4]+=len[j];
					}else{
						v[4]=7;
						v.pb(0);
						ans=i;
						break;
					}
				}
			}
		}
		cout<<ans+1<<endl;
	}
}

C++: #include <bits/stdc++.h>

using namespace std;

int n;

int main(){
    while(1){
        cin >> n;
        if(n==0)break;
        vector<string> w(n);
        int tan[] = {5,7,5,7,7};
        for(int i=0;i<n;i++){
            cin >> w[i];
        }
        int j=0;
        int ans=0;
        int sum=0;
        for(int i=0;i<n;i++){
            sum += w[i].size();
            if(sum > tan[j]){
                sum = w[i].size();
                j=0;
                ans=i;
            }
            if(sum < tan[j])continue;
            if(sum == tan[j]){
                if(j==4)break;
                else {
                    j++;
                    sum = 0;
                }
            }
        }
        cout << ans+1 << endl;

    }
}

C++: #include<iostream>
#include<string>
#include<cstdio>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
#include<cmath>
#include<cstring>
#include<utility>
#include<set>
#include<stack>
#include<complex>
#define vi vector<int>
#define vvi vector<vector<int> >
#define ll long long int
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vb vector<bool>
#define vc vector<char>
#define vs vector<string>
#define ld long double
#define INF 1e9
#define EPS 0.0000000001
#define rep(i,n) for(int i=0;i<n;i++)
#define CC puts("-------ok--------");
#define all(in) in.begin(), in.end()
#define bv vector<bool>
using namespace std;
typedef pair<int, int>PI;
using namespace std;
#define MAX  999999
int main(){
    int n;
    while(cin >> n,n){
         vi v(10000,0);
        rep(i, n){string s; cin >> s; v[i] = (int)s.length();}
        int ans = 0;
        rep(i, n){
            int temp = 0; int array[] = {5,7,5,7,7}; int counter = 0;
            ans = i+1;
            for(int k = i;k<n;k++){
                temp+=v[k];
                if(temp == array[counter])
                {   temp = 0; counter++;
                    if(temp == 0 && counter == 5) goto L;
                }
            }
        }
    L:cout << ans << endl;
        ans = 0;
        
    }
}

C++: #include <iostream>
#include <string>
#include <cstdio>
using namespace std;
int n;

int check(int num,int start, string w[40]){
  int count = start;
  bool flag = true;
  while(flag){
    if(count >= n){
      flag = false;
      break;
    }
    else if(num - w[count].size() == 0){
      count++;
      break;
    }
    else if(num - w[count].size() > 0){
      num -= w[count].size();
      count++;
      continue;
    }
    else {
      flag = false;
      break;
    }
  }
  if(flag) return count;
  else return -1;
}

int main(){
  string w[40];
  while(true){
    cin >> n;
    //cout << "n="<<n << endl;
    if(n == 0) break;

    for(int i = 0; i < n; i++){
      cin >> w[i];
    }

    for(int i = 0; i < n - 4; i++){
      int point = i;

      point = check(5, i, w);
      if(point == -1) continue;
      point = check(7, point, w);
      if(point == -1) continue;
      point = check(5, point, w);
      if(point == -1) continue;
      point = check(7, point, w);
      if(point == -1) continue;
      point = check(7, point, w);
      if(point != -1){
         cout << i+1 << endl;
         break;
      }
    }
  }
  return 0;
}