function Main(input) {
  input = input.split("\n");
  var d = parseInt(input[0].split(" ")[0]);
  var g = parseInt(input[0].split(" ")[1]);
  p = new Array(d).fill(0);
  c = new Array(d).fill(0);

  for(i=0;i<d;i++){
    p[i]=parseInt(input[i+1].split(" ")[0]);
    c[i]=parseInt(input[i+1].split(" ")[1]);
  }
  a = new Array(d).fill(0);
  for(i=0;i<d;i++){
    a[i]=((i+1)*100)*p[i]+c[i];
  }
  var min = 10000000;
  m = new Array(d).fill(0);
  function f(a, min, d, d2,x,n,m,i2){
    for(i2=0;i2<2;i2++){
      var o2 = x;
      x += a[d2-1]*(i2);
      var o = n;
      n += p[d2-1]*(i2);
      m[d-d2] = 2*(i2);
      if(d2>=d){
        if(x<=g&&Math.ceil((g-x)/((d-m.indexOf(0))*100))<=p[d-m.indexOf(0)-1]){
          n += Math.ceil((g-x)/((d-m.indexOf(0))*100));
        }else if(x>=g){
          n= n;
        }else{
          n = 10000000;
        }
        min = Math.min(min,n);
        n=o;
        x=o2;
      }else{
        min=f(a,min,d,d2+1,x,n,m,i2);
      }
    }
    return min;
  }
  for(i1=0;i1<2;i1++){
    var x=0;
    var n=0;
    x += a[0]*(i1);
    n += p[0]*(i1);
    m[d-1] = 1*(i1);
    if(d<2){
      if(x<=g){
        n += Math.ceil((g-x)/((d-m.indexOf(0))*100));
      }
      min = Math.min(min,n);
    }else{
      min=f(a,min,d,2,x,n,m,0);
    }
  }
  console.log('%s', min);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));