fix mint, comb

Author: atcoder-live

comb.cpp

@@ -4,6 +4,7 @@
 struct combination {
   vector<mint> fact, ifact;
   combination(int n):fact(n+1),ifact(n+1) {
+    assert(n < mod);
     fact[0] = 1;
     for (int i = 1; i <= n; ++i) fact[i] = fact[i-1]*i;
     ifact[n] = fact[n].inv();

mint.cpp

@@ -5,7 +5,7 @@
 const int mod = 1000000007;
 struct mint {
   ll x; // typedef long long ll;
-  mint(ll x=0):x(x%mod){}
+  mint(ll x=0):x((x%mod+mod)%mod){}
   mint& operator+=(const mint a) {
     if ((x += a.x) >= mod) x -= mod;
     return *this;