#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define RD(v) int v=0;{int t;while(t=*rp++-48,t>=0)v=v*10+t;}
#define RDL(v) long v=0;{int t;while(t=*rp++-48,t>=0)v=v*10+t;}

#define MD 1000000007

main(){
	char*rp=mmap(0l,4096l<<10,1,2,0,0ll);
	long a=0;
	while(*rp++!=10);
	do{
		RDL(c);
		c=c+1>>1;
		c%=MD;
		RDL(d);
		a+=d%MD*c%MD;
	}while(*rp);
	a%=MD;
	char wbuf[16],*wp=wbuf+16;
	while(*--wp=a%10+48,a/=10);
	write(1,wp,wbuf+16-wp);
	_exit(0);
}