delete pics to save space

7.2891.cpp

@@ -0,0 +1,35 @@
+#include<cstdio>
+typedef long long LL;
+LL exgcd(LL a,LL b,LL &x,LL &y)
+{
+	if(!b) { x=1; y=0; return a; }
+	LL d=exgcd(b,a%b,y,x);
+	y-=x*(a/b);
+	return d;
+}
+int n,fail;
+LL a,m,lcm,res,k,d,x,y;
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	while(scanf("%d%lld%lld",&n,&m,&a)==3)
+	{
+		lcm=m; res=a; fail=0;
+		//printf("lcm=%d now=%d\n",lcm,res);
+		for(int i=2;i<=n;i++)
+		{
+			scanf("%lld%lld",&m,&a);
+			a=(a-res%m+m)%m;// printf("i=%d a=%d\n",i,a);
+			d=exgcd(lcm,m,x,y);// printf("d=%d x=%d y=%d\n",d,x,y);
+			if(a%d) fail=1;
+			else k=x*(a/d)%m;
+			res=res+k*lcm;
+			lcm=lcm/d*m;
+			res=(res%lcm+lcm)%lcm;
+		}
+		printf("%lld\n",fail?-1:res);
+	}
+	return 0;
+}