#include<stdio.h>
 
int main(){
	int D[61], E[61];
	int i,N,M,r;
	char L;
 
    //enquanto existem valores sendo fornecidos
	while(scanf("%d", &N)>=0){
		r=0;
		//preenche os dois vetores com zeros
		for(i=0; i<61; i++){
			D[i] = 0;
			E[i] = 0;
		}
		//enquanto tiver botas (N > 0) faça
		while(N--){
			scanf("%d %c", &M, &L);
			if(L=='E') {
                            E[M]++;
                        } else {
                    	    D[M]++;
                        }
			if(E[M] && D[M]){
			    E[M]--;
			    D[M]--;
			    r++;
			}
		}
		printf("%d\n", r);
	}
 
	return 0;
}

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NAo0MCBECjQxIEUKNDEgRAo0MCBFCjYKMzggRQozOSBFCjQwIEQKMzggRAo0MCBECjM3IEU=

4
40 D
41 E
41 D
40 E
6
38 E
39 E
40 D
38 D
40 D
37 E