#include <stdio.h>

long a,b,c,T,rez=0;

long ter(long left,long right,long absolutePrecision)
{
long leftThird,rightThird;
    if (right-left < absolutePrecision) return (left+right)/2;
    leftThird = (left*2+right)/3;
    rightThird = (left+right*2)/3;
    if (leftThird < rightThird)
	return ter(leftThird, right, absolutePrecision);
    else
	return ter(left, rightThird, absolutePrecision);
}

int main()
{
freopen("inundatii.in","rt",stdin);
freopen("inundatii.out","wt",stdout);
scanf("%ld", &T);
while (T--)
{
scanf("%ld %ld %ld", &a,&b,&c);
rez+=ter(b,a,c);
}
printf("%ld", rez);
return 0;
}