#line 2 "/Users/kaage/Desktop/ProgrammingWorkspace/library/other/template.hpp"
#define _CRT_SECURE_NO_WARNINGS
#pragma target("avx2")
#pragma optimize("O3")
#pragma optimize("unroll-loops")
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <string.h>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=1;i<=(n);i++)
#define all(V) V.begin(),V.end()
typedef unsigned int uint;
typedef long long lint;
typedef unsigned long long ulint;
typedef std::pair<int, int> P;
typedef std::pair<lint, lint> LP;
constexpr int INF = INT_MAX/2;
constexpr lint LINF = LLONG_MAX/2;
constexpr double eps = DBL_EPSILON;
constexpr double PI=3.141592653589793238462643383279;
template<class T>
class prique :public std::priority_queue<T, std::vector<T>, std::greater<T>> {};
template <class T, class U>
inline bool chmax(T& lhs, const U& rhs) {
	if (lhs < rhs) {
		lhs = rhs;
		return 1;
	}
	return 0;
}
template <class T, class U>
inline bool chmin(T& lhs, const U& rhs) {
	if (lhs > rhs) {
		lhs = rhs;
		return 1;
	}
	return 0;
}
inline lint gcd(lint a, lint b) {
	while (b) {
		lint c = a;
		a = b; b = c % b;
	}
	return a;
}
inline lint lcm(lint a, lint b) {
	return a / gcd(a, b) * b;
}
bool isprime(lint n) {
	if (n == 1)return false;
	for (int i = 2; i * i <= n; i++) {
		if (n % i == 0)return false;
	}
	return true;
}
template<typename T>
T mypow(T a, lint b) {
	T res(1);
	while(b){
		if(b&1)res*=a;
		a*=a;
		b>>=1;
	}
	return res;
}
lint modpow(lint a, lint b, lint m) {
	lint res(1);
	while(b){
		if(b&1){
			res*=a;res%=m;
		}
		a*=a;a%=m;
		b>>=1;
	}
	return res;
}
template<typename T>
void printArray(std::vector<T>& vec) {
	rep(i, vec.size()){
		std::cout << vec[i];
		std::cout<<(i==(int)vec.size()-1?"\n":" ");
	}
}
template<typename T>
void printArray(T l, T r) {
	T rprev = std::prev(r);
	for (T i = l; i != rprev; i++) {
		std::cout << *i << " ";
	}
	std::cout << *rprev << std::endl;
}
LP extGcd(lint a,lint b) {
	if(b==0)return {1,0};
	LP s=extGcd(b,a%b);
	std::swap(s.first,s.second);
	s.second-=a/b*s.first;
	return s;
}
LP ChineseRem(const lint& b1,const lint& m1,const lint& b2,const lint& m2) {
	lint p=extGcd(m1,m2).first;
	lint tmp=(b2-b1)*p%m2;
	lint r=(b1+m1*tmp+m1*m2)%(m1*m2);
	return std::make_pair(r,m1*m2);
}
template<typename F>
inline constexpr decltype(auto) lambda_fix(F&& f){
	return [f=std::forward<F>(f)](auto&&... args){
		return f(f,std::forward<decltype(args)>(args)...);
	};
}
#line 2 "main.cpp"
int N,M,w[8],l[100010],v[100010];
std::vector<P> vec;
int main(){
	std::cin>>N>>M;
	rep(i,N)std::cin>>w[i];
	rep(i,M){
		std::cin>>l[i]>>v[i];
		vec.emplace_back(v[i],l[i]);
	}
	if(*std::min_element(v,v+M)<*std::max_element(w,w+N)){
		puts("-1");
		return 0;
	}
	vec.emplace_back(0,0);
	std::sort(all(vec));
	rep(i,M)chmax(vec[i+1].second,vec[i].second);
	std::vector<int> pm(N);
	std::iota(all(pm),0);
	int ans=INF;
	do{
		std::vector<int> dp(N);
		rep(i,N-1){
			int weight=w[pm[i]];
			for(int j=i+1;j<N;j++){
				weight+=w[pm[j]];
				chmax(dp[j],dp[i]+std::prev(std::lower_bound(all(vec),P{weight,0}))->second);
			}
		}
		chmin(ans,dp[N-1]);
	}while(std::next_permutation(all(pm)));
	std::cout<<ans<<std::endl;
	return 0;
}
#include <algorithm>
#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <cmath>

using namespace std;
using ll = long long;
using ull = unsigned long long;

constexpr ll LLINF {1001002003004005006};//ll = 9*LLINF
constexpr int INTINF {1000000000};//int = 2*INTINF

#define  rep(i,n)   for(int i = 0; i < (n); ++i)
#define rrep(i,n)   for(int i = 1; i <= (n); ++i)
#define drep(i,n)   for(int i = (n)-1; i >= 0; --i)
#define srep(i,s,t) for(int i = s; i < t;  ++i)

template<typename T>
void maxs(T& x, T&& y) {
  x=std::max(x,y);
}
template<typename T>
void maxs(T& x, T& y) {
  x=std::max(x,y);
}

template<typename T>
void mins(T& x, T&& y) {
  x=std::min(x,y);
}
template<typename T>
void mins(T& x, T& y) {
  x=std::min(x,y);
}

int main() {
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);

  ll n; cin >> n;
  const std::string S {"110"};
  std::string T; cin >> T;
  constexpr ll const_n {30000000000};
  //constexpr ll const_n {3};

  ll ans {};

  rep(i, 3) {
    bool is_find {true};
    rep(j, n) {
      if (T[j] != S[(i+j)%3]) {
        is_find = false;
        break;
      }
    }
    if (is_find == true) {
      ans += (const_n - n- i) / S.size() + 1;
    }
  }
  cout << ans << '\n';
}
