#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

char *p1, *p2, buf[100000];

#define nc() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 100000, stdin), p1 == p2) ? EOF : *p1 ++ )

ll rd() {
	ll x = 0;
	int f = 1;
	char c = nc();
	while (c < 48) {
		if (c == '-')
			f = -1;
		c = nc();
	}
	while (c > 47) {
		x = (((x << 2) + x) << 1) + (c ^ 48), c = nc();
	}
	return x * f;
}

int a[20], cnt, b[20];

ll C[20][20];

void init() {
	C[0][0] = 1;
	for (int i = 1; i <= 19; i ++ ) {
		C[i][0] = 1;
		for (int j = 1; j <= i; j ++ ) {
			C[i][j] = (C[i - 1][j] + C[i - 1][j - 1]) % 10;
		}
	}
}

inline ll f(ll x) {
	cnt = 0;
	while (x) {
		a[ ++ cnt] = x % 10;
		x /= 10;
	}
	ll mdl = 0;
	for (int i = cnt; i >= 2; i -- ) {
		(mdl += C[cnt - 1][i - 1] * a[i] % 10) %= 10;
	}
	return mdl;
}

// inline ll f(ll x) {
// 	cnt = 0;
// 	for (; x; x /= 10)
// 		a[cnt ++ ] = x % 10;
// 	reverse(a, a + cnt);
// 	while(cnt != 1) {
// 		int m = 0;
// 		for (int i = 1; i < cnt; i ++ ) {
// 			int c = (a[i] + a[i-1]) % 10;
// 			if(!m && !c) continue;
// 			b[m ++ ] = c;
// 		}
// 		if (!m)
// 			b[m ++ ] = 0;
// 		cnt = m;
// 		for (int i = 0; i < cnt; i ++ )
// 			a[i] = b[i];
// 	}
// 	return a[0];
// }

ll calc(ll x) {
	if (x < 10ll) {
		return (x + 1) * x / 2;
	}
	ll ans = x / 10 * 45;
	ll mdl = f(x / 10 * 10);
	// cout << mdl << endl ;
	int tmp = x % 10;
	for (int i = 0; i <= tmp; i ++ ) {
		ans += (mdl + i) % 10;
	}
	return ans;
}

int main() {
	int T = rd();
	init();
	while (T -- ) {
		ll l = rd(), r = rd();
		printf("%llu\n", calc(r) - calc(l - 1));
	}
	return 0;
}