#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; template struct modint { private: unsigned int value; static constexpr int mod() {return m;} public: constexpr modint(const long long x = 0) noexcept { long long y = x; if(y < 0 || y >= mod()) { y %= mod(); if(y < 0) y += mod(); } value = (unsigned int)y; } static constexpr int get_mod() noexcept {return m;} static constexpr int primitive_root() noexcept { assert(m == 998244353); return 3; } constexpr unsigned int val() noexcept {return value;} constexpr modint &operator+=(const modint &other) noexcept { value += other.value; if(value >= mod()) value -= mod(); return *this; } constexpr modint &operator-=(const modint &other) noexcept { unsigned int x = value; if(x < other.value) x += mod(); x -= other.value; value = x; return *this; } constexpr modint &operator*=(const modint &other) noexcept { unsigned long long x = value; x *= other.value; value = (unsigned int) (x % mod()); return *this; } constexpr modint &operator/=(const modint &other) noexcept { return *this *= other.inverse(); } constexpr modint inverse() const noexcept { assert(value); long long a = value,b = mod(),x = 1,y = 0; while(b) { long long q = a/b; a -= q*b; swap(a,b); x -= q*y; swap(x,y); } return modint(x); } constexpr modint power(long long N) const noexcept { assert(N >= 0); modint p = *this,ret = 1; while(N) { if(N & 1) ret *= p; p *= p; N >>= 1; } return ret; } constexpr modint operator+() {return *this;} constexpr modint operator-() {return modint() - *this;} constexpr modint &operator++(int) noexcept {return *this += 1;} constexpr modint &operator--(int) noexcept {return *this -= 1;} friend modint operator+(const modint& lhs, const modint& rhs) {return modint(lhs) += rhs;} friend modint operator-(const modint& lhs, const modint& rhs) {return modint(lhs) -= rhs;} friend modint operator*(const modint& lhs, const modint& rhs) {return modint(lhs) *= rhs;} friend modint operator/(const modint& lhs, const modint& rhs) {return modint(lhs) /= rhs;} friend ostream &operator<<(ostream &os,const modint &x) {return os << x.value;} }; /* using mint = modint<998244353>; */ using mint = modint<1000000007>; void Main() { int N,M; cin >> N >> M; vector>> G(N + 1); vector> RG(N + 1); for(int i = 0;i < M;i++) { int u,v,l,a; cin >> u >> v >> l >> a; G[v].push_back(make_tuple(u,l,a)); RG[u].push_back(v); } vector vis(N + 1),rvis(N + 1); { auto dfs = [&](auto dfs,int u) -> void { vis[u] = 1; for(const auto &[v,l,a] : G[u]) { if(vis[v]); else { dfs(dfs,v); } } }; auto rdfs = [&](auto dfs,int u) -> void { rvis[u] = 1; for(int v : RG[u]) { if(rvis[v]); else { dfs(dfs,v); } } }; /* dfs(dfs,N); */ /* rdfs(rdfs,0); */ } vector dp(N + 1),way(N + 1); vector seen(N + 1),fin(N + 1); bool inf = false; auto dfs = [&](auto dfs,int u) -> void { if(!vis[u] || !rvis[u]) { return; } seen[u] = 1; if(u == 0) { dp[u] = 0; way[u] = 1; } for(const auto &[v,l,a] : G[u]) { if(seen[v]) { if(fin[v]); else { inf = true; return; } } else { dfs(dfs,v); if(inf) { return; } } dp[u] += (dp[v] + l * way[v]) * a; way[u] += way[v] * a; } fin[u] = 1; return; }; dfs(dfs,N); if(inf) { cout << "INF\n"; } else { cout << dp[N] << "\n"; } } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int tt = 1; /* cin >> tt; */ while(tt--) Main(); }