You have an integer variable x.
Initially, x=0.
Some person gave you a string S of length N, and using the string you performed the following operation N times.
In the i-th operation, you incremented the value of x by 1 if S_i=I, and decremented the value of x by 1 if S_i=D.
Find the maximum value taken by x during the operations (including before the first operation, and after the last operation).

-----Constraints-----
- 1≤N≤100
- |S|=N
- No characters except I and D occur in S.

-----Input-----
The input is given from Standard Input in the following format:
N
S

-----Output-----
Print the maximum value taken by x during the operations.

-----Sample Input-----
5
IIDID

-----Sample Output-----
2

After each operation, the value of x becomes 1, 2, 1, 2 and 1, respectively. Thus, the output should be 2, the maximum value.

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