function main(input) {
  var D = input[0].split(" ")[0]-0;
  var G = input[0].split(" ")[1]-0;
  var lines = [];
  var pafemap = [];
  for(var i=1;i<=D;i++){
    lines.push(input[i].split(" ").map(v=>v-0));
    pafemap.push(i*100*lines[i-1][0]+lines[i-1][1]);
  }
  var ans = 100*100;
  for(var i=0;i<Math.pow(2,D);i++){
    var st = ("0000000000" + i.toString(2)).slice(-D);
    var score = 0;
    var nums = 0;
    var npafe = [];
    for(var j=0;j<st.length;j++){
      if(st[j]=="1"){
        score += pafemap[j];
        nums += lines[j][0];
      }else{
        npafe.push({
          i: j+1, num: lines[j][0],
        });
      }
    }
    if(score<G){
      npafe.reverse();
      for(var j=0;j<npafe.length;j++){
        var num = npafe[j].num-1;
        var scr = npafe[j].i*100;
        if(score+scr*num<G){
          score+=scr*num;
          nums+=num;
        }else{
          var n = Math.min(num, Math.ceil((G-score)/scr));
          score+=scr*n;
          nums+=n;
          break;
        }
      }
    }
    if(score>=G)
      ans = Math.min(ans, nums);
  }
  console.log(ans);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"))
