import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.Arrays; import java.util.NoSuchElementException; public class Main { public static void main(String[] args) { new Main().run(); } final long p=(long)1e9+7; class Edge { int src, dst; long dist, cnt; public Edge(int src, int dst, long dist, long cnt) { this.src = src; this.dst = dst; this.dist = dist; this.cnt = cnt; } } void run() { FastScanner sc=new FastScanner(); int N=sc.nextInt()+1; int M=sc.nextInt(); ArrayList[] g=new ArrayList[N]; ArrayList[] grev=new ArrayList[N]; for (int i=0;i(); for (int i=0;i(); for (int i=0;i[] g, boolean[] valid) { valid[cur]=true; for (Edge e:g[cur]) { if (!valid[e.dst]) dfs0(e.dst,g,valid); } } void dfs(int cur, ArrayList[] g, long[] ans, int[] state, long[] cnt, boolean[] ok) { state[cur]=1; for (Edge e:g[cur]) if (ok[e.dst]) { if (state[e.dst]==1) { System.out.println("INF"); System.exit(-1); } dfs(e.dst,g,ans,state,cnt,ok); } for (Edge e:g[cur]) if (ok[e.dst]){ cnt[cur]+=cnt[e.dst]*e.cnt%p; cnt[cur]%=p; ans[cur]+=ans[e.dst]*e.cnt+cnt[e.dst]*e.cnt%p*e.dist%p; ans[cur]%=p; } state[cur]=2; } void tr(Object...objects) { System.out.println(Arrays.deepToString(objects)); } } class FastScanner { private final InputStream in = System.in; private final byte[] buffer = new byte[1024]; private int ptr = 0; private int buflen = 0; private boolean hasNextByte() { if (ptr < buflen) { return true; } else { ptr = 0; try { buflen = in.read(buffer); } catch (IOException e) { e.printStackTrace(); } if (buflen <= 0) { return false; } } return true; } private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1; } private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126; } public boolean hasNext() { while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte(); } public String next() { if (!hasNext()) throw new NoSuchElementException(); StringBuilder sb = new StringBuilder(); int b = readByte(); while (isPrintableChar(b)) { sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } public long nextLong() { if (!hasNext()) throw new NoSuchElementException(); long n = 0; boolean minus = false; int b = readByte(); if (b == '-') { minus = true; b = readByte(); } if (b < '0' || '9' < b) { throw new NumberFormatException(); } while (true) { if ('0' <= b && b <= '9') { n *= 10; n += b - '0'; } else if (b == -1 || !isPrintableChar(b)) { return minus ? -n : n; } else { throw new NumberFormatException(); } b = readByte(); } } public int nextInt() { long nl = nextLong(); if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException(); return (int) nl; } public double nextDouble() { return Double.parseDouble(next()); } }