function Main(s) {
  var s = s.split("\n");
  var d = s[0].split(" ")[0]*1, g = s[0].split(" ")[1]/100;
  var p_c = s.map(e => e.split(" ").map(e => e*1));
  var dp = new Array(d+1);
  p_c = [[0,0]].concat(p_c.map((e) => [e[0], e[1]/100]).slice(1, d+1));
  for (var i = 0; i < d + 1; i++) {
    dp[i] = new Array(p_c[i][0]);
    for (var j = 0; j <= p_c[i][0]; j++) {
      dp[i][j] = new Array(g+1).fill(Infinity);
    }
  }
  for (var i = 1; i < d + 1; i++) {
    for (var j = 1; j <= p_c[i][0]; j++) {
      for (var k = 0; k < g+1; k++) {
        if (k <= j * i) {
          dp[i][j][k] = j;
        }
        if (j === p_c[i][0] && k <= j * i + p_c[i][1]) {
          dp[i][j][k] = j;
        }
        if (k <= dp[i-1][p_c[i-1][0]][k-(j*i)] + j * i) {
          dp[i][j][k] = Math.min(dp[i][j][k], dp[i-1][p_c[i-1][0]][k-(j*i)] + j);
        }
        if (j === p_c[i][0] && k <= dp[i-1][p_c[i-1][0]][k-(j*i+p_c[i][1])] + j*i + p_c[i][1]) {
          dp[i][j][k] = Math.min(dp[i][j][k], dp[i-1][p_c[i-1][0]][k-(j*i+p_c[i][1])] + j)
        }
        dp[i][j][k] = Math.min(dp[i][j][k], dp[i][j-1][k], dp[i-1][p_c[i-1][0]][k])
      }
    }
  }
  console.log(dp[d][p_c[d][0]][g]);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
