delete pics to save space

1.4777.cpp

@@ -0,0 +1,49 @@
+#include<cstdio>
+#include<algorithm>
+using namespace std;
+typedef long long LL;
+const int maxn=100005;
+LL exgcd(LL a,LL b,LL &x,LL &y)
+{
+	if(b==0) { x=1; y=0; return a; }
+	LL d=exgcd(b,a%b,x,y);
+	LL z=x; x=y; y=z-(a/b)*y;
+	return d;
+}
+inline LL mmul(LL a, LL b, LL m)
+{
+    LL d=((long double)a/m*b+1e-8);
+    LL r=a*b-d*m;
+    return r<0?r+m:r;
+}
+int n;
+LL ai[maxn],bi[maxn];
+/*
+i=1...n
+x = ai ( mod bi )
+*/
+LL excrt()
+{
+	LL x,y,M=bi[1],res=ai[1];
+	for(int i=2;i<=n;i++)
+	{
+		LL a=M,b=bi[i],c=((ai[i]-res)%b+b)%b;
+		LL gcd=exgcd(a,b,x,y),b_g=b/gcd;
+		if(c%gcd) return -1;
+		x=mmul(x,c/gcd,b_g);
+		res+=x*M;
+		M*=b_g;//M=lcm(M,b)
+		res=(res%M+M)%M;
+	}
+	return (res%M+M)%M;
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	scanf("%d",&n);
+	for(int i=1;i<=n;i++) scanf("%lld%lld",&bi[i],&ai[i]);
+	printf("%lld\n",excrt());
+	return 0;
+}