Answer: N=102.
First solution. Suppose N≤101. Cut the stick into N−1 pieces of length 1 cm and one piece of length (201−N) cm. From this set, it is impossible to form a rectangle, since each side of the rectangle is less than the semiperimeter, and therefore the piece of length 201−N≥100 cm cannot be part of any side. Thus, N≥102.
Let us show that for N=102 it is possible to form a rectangle. For this, note that among all the pieces there will be two of length 1 cm. Indeed, if this were not the case, the total length of the pieces would be at least 2⋅101+1=203 cm, which is not true.
Set aside these two pieces. Let the lengths of the remaining pieces be a1,a2,…,a100 cm, then a1+a2+⋯+a100=198. Among the 100 numbers A1=a1,A2=a1+a2,A3=a1+a2+a3,…,A100=a1+a2+⋯+a100, there will be two with the same remainder when divided by 99. Let these be Ak and Aℓ, k<ℓ. The number Aℓ−Ak is strictly greater than zero and strictly less than 198, and it is divisible by 99. Therefore, Aℓ−Ak=99=ak+1+ak+2+⋯+aℓ.
Thus, we have found several pieces with a total length of 99 cm. Set these aside as well. The remaining pieces also have a total length of 99 cm. Therefore, we can form a rectangle of 1×99 cm.
Second solution. Here is another proof that for N=102 it is possible to form a rectangle.
Let the lengths of the pieces, in centimeters, be a1,a2,…,a102. We have a1+a2+⋯+a102=200. Consider a circle of length 200 and mark 102 red points dividing it into arcs of lengths a1,a2,…,a102. These points are some 102 vertices of a regular 200-gon T inscribed in this circle. The vertices of T are divided into pairs of opposite points. There are 100 such pairs, and 102 red points, so among the red points there are two pairs of opposite points.
These two pairs of points divide the circle into two pairs of equal arcs. Thus, we have divided all the pieces into four groups A,B,C,D, with the total lengths in groups A and C, and in groups B and D, being equal. Therefore, we can form a rectangle, using each group to make one side.
Third solution. Here is yet another proof that for N=102 it is possible to form a rectangle. We show how to lay out a rectangle 1×99.
Let ℓ≥2 be the largest among the lengths of all the pieces. Let x be the number of pieces of length 1. Then, besides these x pieces and the piece of length ℓ, there are 101−x pieces, each of length at least 2. Hence ℓ+x+2(101−x)≤200, and x≥ℓ+2. So, there are at least ℓ+2 pieces of length 1. Set aside two pieces of length 1—use them to make two sides of the rectangle, leaving ℓ pieces of length 1.
Start laying out the pieces in order of decreasing length to form one side of length 99. Suppose at some step the row has length L<99, and after adding the next piece of length m it becomes L+m>99. Then remove the last piece of length m, and instead place 99−L pieces of length 1 (this can be done since 99−L<m≤ℓ). Now we have three sides of the rectangle (1, 1, and 99). Laying out the remaining pieces in a row, we get another side of length 99.