import std.stdio, std.conv, std.string, std.array, std.range, std.algorithm, std.container;
import std.math, std.random, std.bigint, std.datetime, std.format;
void main(string[] args){ if(args.length > 1) if(args[1] == "-debug") DEBUG = 1; solve(); }
void log()(){ writeln(""); } void log(T, A ...)(T t, lazy A a){ if(DEBUG) write(t, " "), log(a); } bool DEBUG = 0; 
string read(){ static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res; }
T rtype(T)(){ return read.to!T; } alias rint = rtype!int, rlong = rtype!long, rreal = rtype!real;
T[] rtypes(T)(int n){ return n.iota.map!(i => rtype!T()).array; } alias rint = rtypes!int, rlong = rtypes!long, rreal = rtype!real;

// ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- //

void solve(){
	int d = rint;
	long g  = rlong;
	
	int[] ps;
	long[] cs;
	foreach(k; 0 .. d) ps ~= rint, cs ~= rlong;
	log("ps:", ps, "cs:", cs);
	
	int bestcnt = 100_999;
	foreach(m; 0 .. (1L<<d)){
		int h = 0, tmph = 0;
		long score;
		int cnt;
		foreach(k; 0 .. d){
			if((m & (1L<<k)) == 0){
				tmph = k;
				continue;
			}
			cnt += ps[k];
			score += ps[k] * (k + 1) * 100;
			score += cs[k];
		}
		h = tmph;
		if(score + (ps[h] - 1) * (h + 1) * 100 >= g){
			if(score < g) cnt += (g - score + h) / (h + 1) / 100;
			if(cnt < bestcnt) bestcnt = cnt;
		}
		log("m:", m, "h:", h, "tmph:", tmph, "cnt:", cnt, "score:", score, "bestcnt:", bestcnt);
	}
	
	bestcnt.writeln;
}
