function Main(input){
	input = input.split("\n");
 	const N = parseInt(input[0],10);
  	const S = input[1];
  	const Q = parseInt(input[2],10);
  	let nextInputnum = 3;
  	let Querys = [];
  	for(let i = 0; i < Q ; i++)Querys[i] = input[(nextInputnum + i)];
  	for(let qry of Querys){
    	qry = qry.split(" ");
      	let type = parseInt(qry[0],10);
      	switch(type){
          case 1:
            let i = parseInt(qry[1],10);
            let c = qry[2];
            if(S[i] !== c)S[i] = c;
            break;
          case 2:
            let l = parseInt(qry[1],10);
            let r = parseInt(qry[2],10);
            let result = {};
            if(l <= r && l < N){
              for(l; l < r ;l++;)result[S[(l-1)]] = null;
            }
            console.log(Object.keys(result).length);
            break;
          default:
            break;
        }
    }
}